View source for Fin

{{Short description|Thin component or appendage attached to a larger body or structure}}
{{about|the term in aerodynamics|other uses}}
[[File:Trailing edge NACA 0012.svg|thumb|300px|{{center|Fins typically function as [[foil (fluid mechanics)|foils]] that provide lift or thrust, or provide the ability to steer or stabilize motion in water or air.}}]]

A '''fin''' is a thin appendage or component attached to a larger body or structure.<ref>{{cite book |title=A Dictionary of Aviation |first=David W. |last=Wragg |isbn=978-0-85045-163-4 |edition=first |publisher=Osprey |year=1973 |page=131}}</ref> Fins typically function as [[foil (fluid mechanics)|foils]] that produce [[lift (force)|lift]] or [[thrust]], or provide the ability to steer or stabilize motion while traveling in water, air, or other [[fluids]]. Fins are also used to [[Fin (extended surface)|increase surface areas for heat transfer purposes]], or simply as ornamentation.<ref>[https://web.archive.org/web/20121029054614/http://oxforddictionaries.com/definition/american_english/fin Fin] ''Oxford dictionary''. Retrieved 24 November 2012.</ref><ref>[http://www.merriam-webster.com/dictionary/fin Fin] {{Webarchive|url=https://web.archive.org/web/20201126080311/https://www.merriam-webster.com/dictionary/fin |date=2020-11-26 }} ''Merriam-Webster dictionary''. Retrieved 24 November 2012.</ref>

Fins first evolved on [[fish]] as a means of locomotion. [[Fish fin]]s are used to generate [[thrust]] and control the subsequent motion. Fish and other aquatic animals, such as [[cetaceans]], actively propel and steer themselves with [[pectoral fin|pectoral]] and [[Caudal fin|tail fins]]. As they swim, they use other fins, such as [[dorsal fin|dorsal]] and [[anal fin]]s, to achieve stability and refine their maneuvering.<ref name=Sfakiotakis /><ref name=Helfman>Helfman G, Collette BB, Facey DE and Bowen BW (2009) [http://limnology.wisc.edu/courses/zoo510/2009/helfman_ch8.pdf "Functional morphology of locomotion and feeding"] {{webarchive|url=https://web.archive.org/web/20150602082907/http://limnology.wisc.edu/courses/zoo510/2009/helfman_ch8.pdf |date=2015-06-02 }} Chapter 8, pp. 101–116. In:''The Diversity of Fishes: Biology'', John Wiley & Sons. {{ISBN|9781444311907}}.</ref>

The fins on the tails of cetaceans, [[Ichthyosauria|ichthyosaurs]], [[metriorhynchids]], [[mosasaurs]] and [[plesiosaurs]] are called '''flukes'''.

==Thrust generation==
Foil shaped fins generate [[thrust]] when moved, the lift of the fin sets water or air in motion and pushes the fin in the opposite direction. Aquatic animals get significant [[thrust]] by moving fins back and forth in water. Often the [[Caudal fin|tail fin]] is used, but some aquatic animals generate thrust from [[pectoral fins]].<ref name=Sfakiotakis /> Fins can also generate thrust if they are rotated in air or water. [[Turbine]]s and [[propeller]]s (and sometimes [[Mechanical fan|fans]] and [[pump]]s) use a number of rotating fins, also called foils, wings, arms or blades.  Propellers use the fins to translate torquing force to lateral thrust, thus propelling an aircraft or ship.<ref>Carlton, John (2007) [https://books.google.com/books?id=QrLNCxzynU4C ''Marine Propellers and Propulsion''] Pages 1–28, Butterworth-Heinemann. {{ISBN|9780750681506}}.</ref> Turbines work in reverse, using the lift of the blades to generate torque and power from moving gases or water.<ref>Soares, Claire (2008) [https://books.google.com/books?id=rTPZp1YCQBkC ''Gas Turbines: A Handbook of Air, Land, and Sea Applications''] {{Webarchive|url=https://web.archive.org/web/20231216095310/https://books.google.com/books?id=rTPZp1YCQBkC |date=2023-12-16 }} Pages 1–23, Butterworth-Heinemann. {{ISBN|9780750679695}}.</ref>

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| header            = Moving fins can provide thrust
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| image1            = Barb gonio 080525 9610 ltn Cf.jpg
| width1            = 122
| alt1              = 
| caption1          = Fish get thrust moving vertical tail fins from side to side.
| image2            = Southern right whale caudal fin-2 no sky.JPG
| width2            = 179
| alt2              = 
| caption2          = [[Cetacean]]s get thrust moving horizontal tail fins up and down.
| image3            = Dasyatis thetidis.jpg
| width3            = 135
| alt3              = 
| caption3          = Stingrays get thrust from large pectoral fins.
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| image1            = Stern of Bro Elisabeth 2.jpg
| width1            = 141
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| caption1          = Ship propeller
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| width2            = 140
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| caption2          = Airplane propeller
| image3            = MAKS-2007-turbine.JPG
| width3            = 156
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| caption3          = Compressor fins (blades)
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{{multiple image
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| image1            = Cavitation Propeller Damage.JPG
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| caption1          = Cavitation damage is evident on this propeller.
| image2            = Thunnus obesus (Bigeye tuna) diagram cropped.GIF
| alt2              = 
| caption2          = {{center|<small>Drawing by Dr Tony Ayling</small><hr />[[Finlet]]s may influence the way a [[vortex]] develops around the tail fin.}}
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[[Cavitation]] can be a problem with high power applications, resulting in damage to propellers or turbines, as well as noise and loss of power.<ref name=Franc>Franc, Jean-Pierre and Michel, Jean-Marie (2004) [https://books.google.com/books?id=QJOQYa_oo24C ''Fundamentals of Cavitation''] {{Webarchive|url=https://web.archive.org/web/20231216095310/https://books.google.com/books?id=QJOQYa_oo24C |date=2023-12-16 }} Springer. {{ISBN|9781402022326}}.</ref> Cavitation occurs when negative pressure causes bubbles (cavities) to form in a liquid, which then promptly and violently collapse. It can cause significant damage and wear.<ref name=Franc /> Cavitation damage can also occur to the tail fins of powerful swimming marine animals, such as dolphins and tuna. Cavitation is more likely to occur near the surface of the ocean, where the ambient water pressure is relatively low. Even if they have the power to swim faster, dolphins may have to restrict their speed because collapsing cavitation bubbles on their tail are too painful.<ref name=hurts>{{cite magazine | last = Brahic | first = Catherine | title = Dolphins swim so fast it hurts | magazine = New Scientist | date = 2008-03-28 | url = https://www.newscientist.com/channel/life/dn13553-dolphins-swim-so-fast-it-hurts.html | access-date = 2008-03-31 | archive-date = 2020-11-09 | archive-url = https://web.archive.org/web/20201109040122/https://www.newscientist.com/article/dn13553-dolphins-swim-so-fast-it-hurts/?ignored=irrelevant | url-status = live }}</ref> Cavitation also slows tuna, but for a different reason. Unlike dolphins, these fish do not feel the bubbles, because they have bony fins without nerve endings. Nevertheless, they cannot swim faster because the cavitation bubbles create a vapor film around their fins that limits their speed. Lesions have been found on tuna that are consistent with cavitation damage.<ref name=hurts/>

[[Scombrid]] fishes (tuna, mackerel and bonito) are particularly high-performance swimmers. Along the margin at the rear of their bodies is a line of small rayless, non-retractable fins, known as [[finlet]]s. There has been much speculation about the function  of these finlets. Research done in 2000 and 2001 by Nauen and Lauder indicated that "the finlets have a hydrodynamic effect on local flow during steady swimming" and that "the most posterior finlet is oriented to redirect flow into the developing tail vortex, which may increase thrust produced by the tail of swimming mackerel".<ref>{{cite journal | last1 = Nauen | first1 = JC | last2 = Lauder | first2 = GV | year = 2001a | title = Locomotion in scombrid fishes: visualization of flow around the caudal peduncle and finlets of the Chub mackerel ''Scomber japonicus'' | url = http://jeb.biologists.org/content/204/13/2251.long | journal = Journal of Experimental Biology | volume = 204 | issue = 13 | pages = 2251–63 | doi = 10.1242/jeb.204.13.2251 | pmid = 11507109 | bibcode = 2001JExpB.204.2251N | access-date = 2012-11-20 | archive-date = 2020-08-07 | archive-url = https://web.archive.org/web/20200807052800/http://jeb.biologists.org/content/204/13/2251.long | url-status = live | url-access = subscription }}</ref><ref>{{cite journal | last1 = Nauen | first1 = JC | last2 = Lauder | first2 = GV | year = 2001b | title = Three-dimensional analysis of finlet kinematics in the Chub mackerel ''(Scomber japonicus)'' | journal = The Biological Bulletin | volume = 200 | issue = 1 | pages = 9–19 | doi = 10.2307/1543081 | pmid = 11249216 | jstor = 1543081 | s2cid = 28910289 | url = https://www.biodiversitylibrary.org/part/10992 | access-date = 2021-05-19 | archive-date = 2020-06-14 | archive-url = https://web.archive.org/web/20200614084947/https://www.biodiversitylibrary.org/part/10992 | url-status = live }}</ref><ref>{{cite journal | last1 = Nauen | first1 = JC | last2 = Lauder | first2 = GV | year = 2000 | title = Locomotion in scombrid fishes: morphology and kinematics of the finlets of the Chub mackerel ''Scomber japonicus'' | url = http://jeb.biologists.org/content/203/15/2247.full.pdf | journal = Journal of Experimental Biology | volume = 203 | issue = 15 | pages = 2247–59 | doi = 10.1242/jeb.203.15.2247 | pmid = 10887065 | bibcode = 2000JExpB.203.2247N | access-date = 2012-11-20 | archive-date = 2020-10-01 | archive-url = https://web.archive.org/web/20201001091120/http://jeb.biologists.org/content/203/15/2247.full.pdf | url-status = live }}</ref>

Fish use multiple fins, so it is possible that a given fin can have a hydrodynamic interaction with another fin. In particular, the fins immediately upstream of the caudal (tail) fin may be proximate fins that can directly affect the flow dynamics at the caudal fin. In 2011, researchers using [[Particle image velocimetry|volumetric imaging]] techniques were able to generate "the first instantaneous three-dimensional views of wake structures as they are produced by freely swimming fishes". They found that "continuous tail beats resulted in the formation of a linked chain of vortex rings" and that "the dorsal and anal fin wakes are rapidly entrained by the caudal fin wake, approximately within the timeframe of a subsequent tail beat".<ref>{{cite journal | last1 = Flammang | first1 = BE | last2 = Lauder | first2 = GV | last3 = Troolin | first3 = DR | last4 = Strand | first4 = TE | year = 2011 | title = Volumetric imaging of fish locomotion | url = http://intl-rsbl.royalsocietypublishing.org/content/7/5/695.full | journal = Biology Letters | volume = 7 | issue = 5 | pages = 695–698 | doi = 10.1098/rsbl.2011.0282 | pmid = 21508026 | pmc = 3169073 | access-date = 2012-11-21 | archive-date = 2016-03-04 | archive-url = https://web.archive.org/web/20160304031235/http://intl-rsbl.royalsocietypublishing.org/content/7/5/695.full | url-status = live }}</ref>

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==Motion control==
[[File:Orca porpoising.jpg|thumb|right|{{center|Fins are used by aquatic animals, such as this [[orca]], to generate thrust and control the subsequent motion.<ref>* {{cite journal | last1 = Fish | first1 = FE | year = 2002 | title = Balancing requirements for stability and maneuverability in cetaceans | journal = Integrative and Comparative Biology | volume = 42 | issue = 1| pages = 85–93 | doi = 10.1093/icb/42.1.85 | pmid=21708697| doi-access = free }}</ref><ref>* {{cite journal | last1 = Fish | first1 = FE | last2 = Lauder | first2 = GV | s2cid = 4983205 | year = 2006 | title = Passive and active flow control by swimming fishes and mammals | journal = Annual Review of Fluid Mechanics | volume = 38 | issue = 1| pages = 193–224 | doi = 10.1146/annurev.fluid.38.050304.092201 | bibcode = 2006AnRFM..38..193F }}</ref>}}]]

Once motion has been established, the motion itself can be controlled with the use of other fins.<ref name=Sfakiotakis /><ref name=Perez /><ref name=McClamroch /> Boats control direction (yaw) with fin-like rudders, and roll with stabilizer and keel fins.<ref name=Perez>Perez, Tristan (2005) [https://books.google.com/books?id=lxlO3d2srAIC ''Ship Motion Control: Course Keeping and Roll Stabilisation Using Rudder and Fins''] {{Webarchive|url=https://web.archive.org/web/20231216095310/https://books.google.com/books?id=lxlO3d2srAIC |date=2023-12-16 }} Springer. {{ISBN|9781852339593}}.</ref> Airplanes achieve similar results with small specialised fins that change the shape of their wings and tail fins.<ref name=McClamroch>McClamroch, N Harris (2011) [https://books.google.com/books?id=DKK7m8o7_ZkC&pg=PA58 ''Steady Aircraft Flight and Performance''] {{Webarchive|url=https://web.archive.org/web/20231216095310/https://books.google.com/books?id=DKK7m8o7_ZkC&pg=PA58#v=onepage&q&f=false |date=2023-12-16 }}  Page 2–3, Princeton University Press. {{ISBN|9780691147192}}.</ref>

{{multiple image
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| header            = Specialised fins are used to control motion
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| image1            = Rotations.png
| width1            = 221
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| caption1          = Fish, boats and airplanes need control of three degrees of [[Degrees of freedom (mechanics)|rotational freedom]].<ref name=Magnuson>Magnuson JJ (1978) [https://books.google.com/books?id=wnjnyAafAzUC&pg=PA239 "Locomotion by scombrid fishes: Hydromechanics, morphology and behavior"] {{Webarchive|url=https://web.archive.org/web/20231216095310/https://books.google.com/books?hl=en&lr=&id=wnjnyAafAzUC&oi=fnd&pg=PA239#v=onepage&q&f=false |date=2023-12-16 }} in ''Fish Physiology'', Volume 7: Locomotion, WS Hoar and DJ Randall (Eds) Academic Press. Page 240–308. {{ISBN|9780123504074}}.</ref><ref>[http://www.pomorci.com/Zanimljivosti/Ship's%20movements%20at%20sea.pdf Ship's movements at sea]  {{webarchive|url=https://web.archive.org/web/20111125015923/http://www.pomorci.com/Zanimljivosti/Ship%27s%20movements%20at%20sea.pdf |archive-url=https://web.archive.org/web/20100821040522/http://www.pomorci.com/Zanimljivosti/Ship's%20movements%20at%20sea.pdf |archive-date=2010-08-21 |url-status=live |date=November 25, 2011 }} Retrieved 22 November 2012.</ref><ref>Rana and Joag (2001) [https://books.google.com/books?id=1kxkdWGa9-cC&pg=PA391 ''Classical Mechanics''] {{Webarchive|url=https://web.archive.org/web/20231216095310/https://books.google.com/books?id=1kxkdWGa9-cC&pg=PA391 |date=2023-12-16 }} Page 391, Tata McGraw-Hill Education. {{ISBN|9780074603154}}.</ref>
| image3            = White shark (cropped).jpg
| width3            = 214
| alt3              = 
| caption3          = The dorsal fin of a white shark contain [[dermal]] fibers that work "like riggings that stabilize a ship's mast", and stiffen dynamically as the shark swims faster to control roll and yaw.<ref>{{cite journal | last1 = Lingham | last2 = Soliar | first2 = T | s2cid = 827610 | year = 2005 | title = Dorsal fin in the white shark, ''Carcharodon carcharias'': A dynamic stabilizer for fast swimming | journal = Journal of Morphology | volume = 263 | issue = 1| pages = 1–11 | doi = 10.1002/jmor.10207 | pmid=15536651}}</ref>
}}
[[File:Great white shark, Carcharodon carcharias.jpg|thumb|Caudal fin of a [[great white shark]]]]

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| image1            = Yacht keel steer.svg
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| caption1          = A [[rudder]] corrects yaw.
| image2            = Yacht keel.svg
| width2            = 117
| alt2              = 
| caption2          = A fin [[keel]] limits roll and sideways drift.
| image3            = Stabilizer1.JPG
| width3            = 200
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| caption3          = Ship [[Stabilizer (ship)|stabilising fins]] reduce roll.
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| image1            = Aileron roll.gif
| width1            = 145
| alt1              = 
| caption1          = [[Aileron]]s control roll.
| image2            = Aileron pitch.gif
| width2            = 145
| alt2              = 
| caption2          = [[Elevator (aircraft)|Elevators]] control pitch.
| image3            = Aileron yaw.gif
| width3            = 145
| alt3              = 
| caption3          = The [[Rudder#Aircraft rudders|rudder]] controls yaw.
}}

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Stabilising fins are used as [[fletching]] on [[arrow (weapon)|arrow]]s and some [[Dart (missile)|darts]],<ref>Vujic, Dragan (2007) [https://books.google.com/books?id=YsiPb2nmYdEC&pg=PA17 ''Bow Hunting Whitetails''] {{Webarchive|url=https://web.archive.org/web/20231216095311/https://books.google.com/books?id=YsiPb2nmYdEC&pg=PA17 |date=2023-12-16 }} Page 17, iUniverse. {{ISBN|9780595432073}}.</ref> and at the rear of some [[bomb]]s, [[missile]]s, [[rocket]]s and self-propelled [[torpedo]]es.<ref>Hobbs, Marvin (2010) [https://books.google.com/books?id=a0TxaTq2rQIC&pg=SA1-PA24 ''Basics of Missile Guidance and Space Techniques'']  Page 24, Wildside Press LLC. {{ISBN|9781434421258}}.</ref><ref>Compon-Hall, Richard (2004) [https://books.google.com/books?id=EEJ6YaMGkV4C&pg=PA50 ''Submarines at War 1939–1945''] {{Webarchive|url=https://web.archive.org/web/20231216095824/https://books.google.com/books?id=EEJ6YaMGkV4C&pg=PA50#v=onepage&q&f=false |date=2023-12-16 }}  Page 50, Periscope Publishing. {{ISBN|9781904381228}}.</ref>  These are typically [[Plane (geometry)|planar]] and shaped like small wings, although [[grid fin]]s are sometimes used.<ref>Khalid M, Sun Y and Xu H (1998) [ftp://ftp.rta.nato.int/Pubfulltext/RTO/MP/.../RTO-MP-005/$MP-005-12.pdf "Computation of Flows Past Grid Fin Missiles"]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}} ''AVT Symposium on Missile Aerodynamics'', Sorrento, Italy.</ref> Static fins have also been used for one satellite, [[GOCE]].

{{multiple image
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 | header            = Static tail fins are used as stabilizers
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 | image1    = Fletching-Arrow-9.jpeg
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 | caption1  = [[Fletching]] on an [[arrow]]
 | image2    = 122 mm raketti Hämeenlinna 2.JPG
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 | caption2  = Asymmetric stabilizing fins impart spin to this Soviet artillery rocket 
 | image3    = USS Essex (LHD-2) launches RIM-7 Sea Sparrow on 6 February 2004 (040206-N-2970T-002).jpg
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 | caption3  = Conventional "planar" fins on a [[RIM-7 Sea Sparrow]] missile
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==Temperature regulation==
Engineering fins are also used as [[Fin (extended surface)|heat transfer fin]]s to regulate temperature in [[heat sink]]s or [[Radiator (heating)|fin radiator]]s.<ref>Siegel R and Howell JR (2002) [https://books.google.com/books?id=O389yQ0-fecC&pg=PA1 ''Thermal Radiation Heat Transfer''] {{Webarchive|url=https://web.archive.org/web/20231216095824/https://books.google.com/books?id=O389yQ0-fecC&pg=PA1#v=onepage&q&f=false |date=2023-12-16 }} Chapter 9: Radiation combined with conduction and convection at boundaries, pp.335–370. Taylor & Francis. {{ISBN|9781560328391}}.</ref><ref>[https://www.britannica.com/EBchecked/topic/207095/fin Fin: Function in aircraft engines] {{Webarchive|url=https://web.archive.org/web/20231216095917/https://prebid-server.rubiconproject.com/setuid?bidder=amx&uid=07484e68-faa3-45a1-83dc-4560ee72f259&do=www.britannica.com |date=2023-12-16 }} ''Encyclopædia Britannica''. Retrieved 22 November 2012.</ref>

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| caption1          = [[Motorbike]]s use fins to [[Cooling fin|cool]] the engine.<ref>Clarke, Massimo (2010) 
[https://books.google.com/books?id=u7U524TamcUC&pg=PA62 ''Modern Motorcycle Technology''] {{Webarchive|url=https://web.archive.org/web/20231216095825/https://books.google.com/books?id=u7U524TamcUC&pg=PA62 |date=2023-12-16 }} Page 62, MotorBooks International. {{ISBN|9780760338193}}.</ref>
| image2            = Oil Heater 5293.jpg
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| caption2          = [[Oil heater]]s convect with fins.
| image4            = Istiophorus_platypterus.jpg
| width4            = 198
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| caption4          = [[Sailfish]] raise their [[dorsal fin]] to cool down or to herd [[schooling fish]].<ref name=Cavendish>[https://books.google.com/books?id=va1ODFo_tdUC&pg=PA332 ''Aquatic Life of the World''] {{Webarchive|url=https://web.archive.org/web/20231216095825/https://books.google.com/books?id=va1ODFo_tdUC&pg=PA332#v=onepage&q&f=false |date=2023-12-16 }} pp. 332–333, Marshall Cavendish Corporation, 2000. {{ISBN|9780761471707}}.</ref><ref>Dement J [http://www.littoralsociety.org/userfiles/doccenter/Species%20Spotlight%20Atlantic%20Sailfish.pdf Species Spotlight: Atlantic Sailfish (''Istiophorus albicans'')] {{webarchive |url=https://web.archive.org/web/20101217230458/http://www.littoralsociety.org/userfiles/doccenter/Species%20Spotlight%20Atlantic%20Sailfish.pdf |date=December 17, 2010 }} ''littoralsociety.org''. Retrieved 1 April 2012.</ref>
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==Ornamentation and other uses==
In biology, fins can have an adaptive significance as sexual ornaments. During courtship, the female [[cichlid]], ''[[Pelvicachromis taeniatus]]'', displays a large and visually arresting purple [[pelvic fin]]. "The researchers found that males clearly preferred females with a larger pelvic fin and that pelvic fins grew in a more disproportionate way than other fins on female fish."<ref>[https://www.sciencedaily.com/releases/2010/10/101007210540.htm Female fish flaunt fins to attract a mate] {{Webarchive|url=https://web.archive.org/web/20190520152144/https://www.sciencedaily.com/releases/2010/10/101007210540.htm |date=2019-05-20 }} ''ScienceDaily''. 8 October 2010.</ref><ref>{{cite journal | last1 = Baldauf | first1 = SA | last2 = Bakker | first2 = TCM | last3 = Herder | first3 = F | last4 = Kullmann | first4 = H | last5 = Thünken | first5 = T | year = 2010 | title = Male mate choice scales female ornament allometry in a cichlid fish | journal = BMC Evolutionary Biology | volume = 10 | issue = 1 | page = 301 | doi = 10.1186/1471-2148-10-301 | pmid = 20932273 | pmc = 2958921 | bibcode = 2010BMCEE..10..301B | doi-access = free }}</ref>

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| header            = Ornamentation
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| image1            = Pelvicachromis taeniatus.jpg
| width1            = 150
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| caption1          = During courtship, the female [[cichlid]], ''[[Pelvicachromis taeniatus]]'', displays her visually arresting purple [[pelvic fin]].
| image2            = Spinosaurus 2020 reconstruction.jpg
| width2            = 246
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| caption2          = ''[[Spinosaurus]]'' may have used its dorsal fin ([[Neural spine sail|sail]]) as a courtship display.<ref name=Stromer15>{{cite journal |last=Stromer |first=E. |author-link=Ernst Stromer |year=1915 |title=Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden ''Spinosaurus aegyptiacus'' nov. gen., nov. spec |journal=Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Klasse |volume=28 |issue=3 |pages=1–32 |language=de |url=http://www.megaupload.com/?d=3KCCC7LS }}{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>{{rp|28}}
| image3            = Cadillac1001.jpg
| width3            = 160
| alt3              = 
| caption3          = [[Car tail fin]]s in the 1950s were largely decorative.<ref>David, Dennis (2001) [https://books.google.com/books?id=VOi0Omb6newC&pg=PA6 ''Fifties Fins''] {{Webarchive|url=https://web.archive.org/web/20231216095826/https://books.google.com/books?id=VOi0Omb6newC&pg=PA6#v=onepage&q&f=false |date=2023-12-16 }} MotorBooks International. {{ISBN|9780760309612}}.</ref>
}}

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Reshaping human feet with [[swim fin]]s, rather like the tail fin of a fish, add thrust and efficiency to the kicks of a [[Human swimming|swimmer]] or [[underwater diving|underwater diver]]<ref>{{cite journal |vauthors=Zamparo P, Pendergast DR, Termin A, Minetti AE|title=Economy and efficiency of swimming at the surface with fins of different size and stiffness |journal=Eur. J. Appl. Physiol. |volume=96 |issue=4 |pages=459–70 |date=March 2006 |pmid=16341874 |doi=10.1007/s00421-005-0075-7|s2cid=34505861 }}</ref><ref>{{cite journal |vauthors=Yamaguchi H, Shidara F, Naraki N, Mohri M |title=Maximum sustained fin-kick thrust in underwater swimming |journal=Undersea Hyperb Med |volume=22 |issue=3 |pages=241–8 |date=September 1995 |pmid=7580765 |url=http://archive.rubicon-foundation.org/2219 |access-date=2008-08-25 |archive-url=https://web.archive.org/web/20110811174931/http://archive.rubicon-foundation.org/2219 |archive-date=2011-08-11 |url-status=usurped }}</ref> [[Surfboard fin]]s provide [[surfer]]s with means to maneuver and control their boards. Contemporary surfboards often have a centre fin and two [[Camber (aerodynamics)|cambered]] side fins.<ref>Brandner PA and Walker GJ (2004) [http://eprints.utas.edu.au/6613/1/AFMC_Brandnerand_Walker_2004_F1.pdf ''Hydrodynamic Performance of a Surfboard Fin''] {{Webarchive|url=https://web.archive.org/web/20201030153346/https://eprints.utas.edu.au/6613/1/AFMC_Brandnerand_Walker_2004_F1.pdf |date=2020-10-30 }} 15th Australasian Fluid Mechanics Conference, Sydney.</ref>

The bodies of [[reef fish]]es are often shaped differently from [[Pelagic fish|open water fishes]]. Open water fishes are usually built for speed, streamlined like torpedoes to minimise friction as they move through the water. Reef fish operate in the relatively confined spaces and complex underwater landscapes of [[coral reef]]s. For this manoeuvrability is more important than straight line speed, so coral reef fish have developed bodies which optimize their ability to dart and change direction. They outwit predators by dodging into fissures in the reef or playing hide and seek around coral heads.<ref name=Alevizon>{{cite book|author=William S. Alevizon|title=Pisces Guide to Caribbean Reef Ecology|url=https://books.google.com/books?id=H9FcAAAAMAAJ|year=1993|publisher=Pisces Books|isbn=978-1-55992-077-3|access-date=2018-04-24|archive-date=2023-12-16|archive-url=https://web.archive.org/web/20231216095827/https://books.google.com/books?id=H9FcAAAAMAAJ|url-status=live}}</ref>

The pectoral and pelvic fins of many reef fish, such as [[butterflyfish]], [[damselfish]] and [[Pomacanthidae|angelfish]], have evolved so they can act as brakes and allow complex maneuvers.<ref name=FMNH>[http://www.flmnh.ufl.edu/fish/education/HowSwim/HowSwim.html Ichthyology] {{Webarchive|url=https://web.archive.org/web/20160105001306/http://www.flmnh.ufl.edu/fish/education/HowSwim/HowSwim.html |date=2016-01-05 }} ''Florida Museum of Natural History''. Retrieved 22 November 2012.</ref> Many reef fish, such as [[butterflyfish]], [[damselfish]] and [[Pomacanthidae|angelfish]], have evolved bodies which are deep and laterally compressed like a pancake, and will fit into fissures in rocks. Their pelvic and pectoral fins are designed differently, so they act together with the flattened body to optimise maneuverability.<ref name=Alevizon /> Some fishes, such as [[puffer fish]], [[filefish]] and [[trunkfish]], rely on pectoral fins for swimming and hardly use tail fins at all.<ref name=FMNH />

{{multiple image
| align             = left
| direction         = horizontal
| width             = 
| header            = Other uses
| header_align      = center
| header_background = 
| image1            = Jetfins reglables.jpg
| width1            = 92
| alt1              = 
| caption1          = [[Swim fin]]s add thrust to the kicks of a human [[Human swimming|swimmer]].
| image2            = Rescue surfboard, Killahoey Strand - geograph.org.uk - 901180.jpg
| width2            = 100
| alt2              = 
| caption2          = [[Surfboard fin]]s allow surfers to maneuver their boards.
| image3            = Shark finning icon.jpg
| width3            = 97
| alt3              = 
| caption3          = In some Asian countries shark fins are a [[Shark finning|culinary delicacy]].<ref>{{cite journal | author = Vannuccini S | year = 1999 | title = Shark utilization, marketing and trade | journal = FAO Fisheries Technical Paper | volume = 389 | url = http://www.fao.org/DOCREP/005/X3690E/x3690e0p.htm | access-date = 2012-11-26 | archive-date = 2017-08-02 | archive-url = https://web.archive.org/web/20170802204244/http://www.fao.org/docrep/005/x3690e/x3690e0p.htm }}</ref>
| image4            = Fernando Alonso won 2012 Malaysian GP.jpg
| width4            = 145
| alt4              = 
| caption4          = In recent years, car fins have evolved into highly functional [[Spoiler (automotive)|spoilers]] and [[Wing (automotive)|wings]].<ref>Ridhwan CZ (2008) [http://umpir.ump.edu.my/581/1/Ridhwan_Che_Zake.pdf Aerodynamics of aftermarket rear spoiler] {{Webarchive|url=https://web.archive.org/web/20111111161147/http://umpir.ump.edu.my/581/1/Ridhwan_Che_Zake.pdf |date=2011-11-11 }} University Malaysia Pahang</ref>
}}
{{clear}}

{{multiple image
| align             = left
| direction         = horizontal
| header            = 
| header_align      = center
| header_background = 
| image1            = Holacanthus ciliaris 1.jpg
| width1            = 138
| alt1              = 
| caption1          = Many [[reef fish]] have pectoral and pelvic fins optimised for flattened bodies.<ref name=Alevizon />
| image2            = Antennarius striatus.jpg
| width2            = 137
| alt2              = 
| caption2          = [[Frog fish]] use their pectoral and pelvic fins to walk along the ocean bottom.<ref>{{cite book |vauthors=Bertelsen E, Pietsch TW|year=1998|title=Encyclopedia of Fishes|publisher= Academic Press|location=San Diego|pages= 138–139|isbn= 978-0-12-547665-2}}</ref>
| image3            = Sailfin flyingfish.jpg
| width3            = 163
| alt3              = 
| caption3          = [[Flying fish]] use enlarged pectoral fins to glide above the surface of the water.<ref>{{cite journal|last=Fish |first=FE |year=1990 |title=Wing design and scaling of flying fish with regard to flight performance |journal=[[Journal of Zoology]] |volume=221 |pages=391–403 |url=http://darwin.wcupa.edu/~biology/fish/pubs/pdf/1990JZWingdesign.pdf |doi=10.1111/j.1469-7998.1990.tb04009.x |issue=3 |archive-url=https://web.archive.org/web/20131020095503/http://darwin.wcupa.edu/~biology/fish/pubs/pdf/1990JZWingdesign.pdf |archive-date=2013-10-20 }}</ref>
}}
{{clear left}}

==Evolution==
[[File:Lampanyctodes hectoris (fins).png|thumb|300px|right|{{center|Aquatic animals typically use fins for [[Aquatic locomotion|locomotion]]<br />(1) pectoral fins (paired), (2) pelvic fins (paired), (3) dorsal fin, (4) adipose fin, (5) anal fin, and (6) caudal (tail) fin.}}]]
{{Quote box
 |title = 
 |quote = Aristotle recognised the distinction between [[Analogous structures|analogous]] and [[homologous structures]], and made the following prophetic comparison:
''"Birds in a way resemble fishes. For birds have their wings in the upper part of their bodies and fishes have two fins in the front part of their bodies. Birds have feet on their underpart and most fishes have a second pair of fins in their under-part and near their front fins."''
 |source = – Aristotle, ''[[Progression of Animals|De incessu animalium]]'' <ref>{{cite journal | last1 = Moore | first1 = John A | year = 1988 | title = Understanding nature—form and function | url = http://www.sicb.org/dl/saawok/449.pdf | journal = American Zoologist | volume = 28 | issue = 2 | pages = 449–584 [485] | doi = 10.1093/icb/28.2.449 | doi-access = free | access-date = 2014-11-08 | archive-date = 2015-09-24 | archive-url = https://web.archive.org/web/20150924101610/http://www.sicb.org/dl/saawok/449.pdf }}</ref>
 |align = right
 |salign = right
 |width = 220px
}}

There is an old theory, proposed by anatomist [[Carl Gegenbaur]], which has been often disregarded in science textbooks, "that fins and (later) limbs evolved from the gills of an extinct vertebrate". Gaps in the fossil record had not allowed a definitive conclusion. In 2009, researchers from the University of Chicago found evidence that the "genetic architecture of gills, fins and limbs is the same", and that "the skeleton of any appendage off the body of an animal is probably patterned by the developmental genetic program that we have traced back to formation of gills in sharks".<ref>[https://www.sciencedaily.com/releases/2009/03/090323212021.htm Evolution Of Fins And Limbs Linked With That Of Gills] {{Webarchive|url=https://web.archive.org/web/20190530052749/https://www.sciencedaily.com/releases/2009/03/090323212021.htm |date=2019-05-30 }} ''ScienceDaily''. 25 March 2009.</ref><ref>{{cite journal | last1 = Gillis | first1 = JA | last2 = Dahn | first2 = RD | last3 = Shubin | first3 = NH | year = 2009 | title = Shared developmental mechanisms pattern the vertebrate gill arch and paired fin skeletons | journal = Proceedings of the National Academy of Sciences | volume = 106 | issue = 14| pages = 5720–5724 | doi=10.1073/pnas.0810959106 | pmid=19321424 | pmc=2667079 | bibcode = 2009PNAS..106.5720G| doi-access = free }}</ref><ref>[http://www.uctv.tv/shows/Wings-Legs-and-Fins-How-Do-New-Organs-Arise-in-Evolution-16421 Wings, legs, and fins: How do new organs arise in evolution?] {{Webarchive|url=https://web.archive.org/web/20200927104725/http://www.uctv.tv/shows/Wings-Legs-and-Fins-How-Do-New-Organs-Arise-in-Evolution-16421 |date=2020-09-27 }} [[Neil Shubin]], University of Chicago.</ref> Recent studies support the idea that gill arches and paired fins are serially homologous and thus that fins may have evolved from gill tissues.<ref>{{Cite journal|last1=Sleight|first1=Victoria A|last2=Gillis|first2=J Andrew|date=2020-11-17|title=Embryonic origin and serial homology of gill arches and paired fins in the skate, Leucoraja erinacea|journal=eLife|language=en|volume=9|article-number=e60635|doi=10.7554/eLife.60635|pmid=33198887|issn=2050-084X|pmc=7671686 |doi-access=free }}</ref>

Fish are the ancestors of all mammals, reptiles, birds and amphibians.<ref>[https://www.sciencedaily.com/releases/2008/09/080922090843.htm "Primordial Fish Had Rudimentary Fingers"] {{Webarchive|url=https://web.archive.org/web/20200927203302/https://www.sciencedaily.com/releases/2008/09/080922090843.htm |date=2020-09-27 }} ''ScienceDaily'', 23 September 2008.</ref> In particular, terrestrial [[tetrapod]]s (four-legged animals) evolved from fish and made their first forays onto land 400 million years ago. They used paired pectoral and pelvic fins for locomotion. The pectoral fins developed into forelegs (arms in the case of humans) and the pelvic fins developed into hind legs.<ref>Hall, Brian K (2007) [https://books.google.com/books?id=Z0YWn5F9sWkC ''Fins into Limbs: Evolution, Development, and Transformation''] University of Chicago Press. {{ISBN|9780226313375}}.</ref> Much of the genetic machinery that builds a walking limb in a tetrapod is already present in the swimming fin of a fish.<ref>[[Neil Shubin|Shubin, Neil]] (2009) [https://books.google.com/books?id=c008kdNwR1cC ''Your inner fish: A journey into the 3.5 billion year history of the human body''] {{Webarchive|url=https://web.archive.org/web/20230317010712/https://books.google.com/books?id=c008kdNwR1cC |date=2023-03-17 }} Vintage Books. {{ISBN|9780307277459}}. [http://www.uctv.tv/search-details.aspx?showID=16412 ''UCTV'' interview] </ref><ref>Clack, Jennifer A (2012) [https://books.google.com/books?id=6Ztrhm8uLQ0C "From fins to feet"] Chapter 6, pages 187–260, ''in:'' ''Gaining Ground, Second Edition: The Origin and Evolution of Tetrapods'', Indiana University Press. {{ISBN|9780253356758}}.</ref>

[[File:Crossopterygii fins tetrapod legs.svg|thumb|180px|left|Comparison between A) the swimming fin of a [[Sarcopterygii|lobe-finned fish]] and B) the walking leg of a [[tetrapod]]. Bones considered to correspond with each other have the same color.]]
[[File:Ichthyosaurus BW.jpg|thumb|right|In a parallel but independent evolution, the ancient reptile ''[[Ichthyosaurus communis]]'' developed fins (or flippers) very similar to fish (or dolphins).]]

In 2011, researchers at [[Monash University]] in Australia used primitive but still living [[lungfish]] "to trace the evolution of pelvic fin muscles to find out how the load-bearing hind limbs of the tetrapods evolved."<ref>[https://www.sciencedaily.com/releases/2011/10/111004180106.htm Lungfish Provides Insight to Life On Land: 'Humans Are Just Modified Fish'] {{Webarchive|url=https://web.archive.org/web/20201111213122/https://www.sciencedaily.com/releases/2011/10/111004180106.htm |date=2020-11-11 }} ''ScienceDaily'', 7 October 2011.</ref><ref>{{cite journal | last1 = Cole | first1 = NJ | last2 = Hall | first2 = TE | last3 = Don | first3 = EK | last4 = Berger | first4 = S | last5 = Boisvert | first5 = CA | display-authors = etal | year = 2011 | title = Development and Evolution of the Muscles of the Pelvic Fin | journal = PLOS Biology | volume = 9 | issue = 10| article-number = e1001168 | doi = 10.1371/journal.pbio.1001168 | pmid = 21990962 | pmc = 3186808 | doi-access = free }}</ref> Further research at the University of Chicago found bottom-walking lungfishes had already evolved characteristics of the walking gaits of terrestrial tetrapods.<ref>[https://www.sciencedaily.com/releases/2011/12/111212153117.htm A small step for lungfish, a big step for the evolution of walking"] {{Webarchive|url=https://web.archive.org/web/20170703172143/https://www.sciencedaily.com/releases/2011/12/111212153117.htm |date=2017-07-03 }} ''ScienceDaily'', 13 December 2011.</ref><ref>{{cite journal | last1 = King | first1 = HM | last2 = Shubin | first2 = NH | last3 = Coates | first3 = MI | last4 = Hale | first4 = ME | year = 2011 | title = Behavioral evidence for the evolution of walking and bounding before terrestriality in sarcopterygian fishes | journal = Proceedings of the National Academy of Sciences | volume = 108 | issue = 52| pages = 21146–21151 | doi=10.1073/pnas.1118669109 | pmid=22160688 | pmc=3248479 | bibcode = 2011PNAS..10821146K| doi-access = free }}</ref>

In a classic example of [[convergent evolution]], the pectoral limbs of [[pterosaur]]s, [[Origin of avian flight|birds]] and [[Bat wing development|bats]] further evolved along independent paths into flying wings. Even with flying wings there are many similarities with walking legs, and core aspects of the genetic blueprint of the pectoral fin have been retained.<ref>{{cite journal | last1 = Shubin | first1 = N | last2 = Tabin | first2 = C | last3 = Carroll | first3 = S | year = 1997 | title = Fossils, genes and the evolution of animal limbs | url = http://genepath.med.harvard.edu/~tabin/Pdfs/Shubin.pdf | journal = Nature | volume = 388 | issue = 6643 | pages = 639–648 | doi = 10.1038/41710 | pmid = 9262397 | archive-url = https://web.archive.org/web/20120916105318/http://genepath.med.harvard.edu/~tabin/Pdfs/Shubin.pdf | archive-date = 2012-09-16 | bibcode = 1997Natur.388..639S | s2cid = 2913898 }}</ref><ref>[http://www.ucmp.berkeley.edu/vertebrates/flight/converge.html Vertebrate flight: The three solutions] {{Webarchive|url=https://web.archive.org/web/20121110035749/http://www.ucmp.berkeley.edu/vertebrates/flight/converge.html |date=2012-11-10 }} University of California. Updated 29 September 2005.</ref>

About 200 million years ago the first mammals appeared. A group of these mammals started returning to the sea about 52 million years ago, thus completing a circle. These are the [[cetacean]]s (whales, dolphins and porpoises). Recent DNA analysis suggests that cetaceans evolved from within the [[even-toed ungulate]]s, and that they share a common ancestor with the [[hippopotamus]].<ref name="ScienceNews">{{Cite web|title=Scientists find missing link between the dolphin, whale and its closest relative, the hippo |date=2005-01-25 |access-date=2007-06-18 |url=http://www.sciencenewsdaily.org/story-2806.html |work=Science News Daily |archive-url=https://web.archive.org/web/20070304214747/http://www.sciencenewsdaily.org/story-2806.html |archive-date=2007-03-04 }}</ref><ref name="DNA">{{Cite journal | title = More DNA support for a Cetacea/Hippopotamidae clade: the blood-clotting protein gene gamma-fibrinogen | author = Gatesy, J. | journal = [[Molecular Biology and Evolution]] | volume = 14 | pages = 537–543 | pmid = 9159931 | issue = 5 | date=1 May 1997 | doi=10.1093/oxfordjournals.molbev.a025790| doi-access = free }}</ref>  About 23 million years ago another group of bearlike land mammals started returning to the sea. These were the [[pinniped]]s (seals).<ref>{{
cite journal
| first1=John J. |last1=Flynn
|last2=Finarelli |first2=John
| title=Molecular Phylogeny of the Carnivora
| journal=Systematic Biology
| year=2005
| volume=54
| pages=317–337
| pmid=16012099
| issue=2
| doi=10.1080/10635150590923326
|last3=Hsu |first3=Johnny
|last4=Nedbal |first4=Michael
|display-authors=1
| doi-access=free
}}</ref> What had become walking limbs in  cetaceans and seals evolved further, independently in a reverse form of convergent evolution, back to new forms of swimming fins. The forelimbs became [[Flipper (anatomy)|flippers]] and, in pinnipeds, the hind limbs became a tail terminating in two fins (the cetacean [[Whale#Evolution|fluke]], conversely, is an entirely new organ).<ref>Felts WJL [https://books.google.com/books?id=KyxELyTDlsQC&pg=PA255 "Some functional and structural characteristics of cetacean flippers and flukes"] {{Webarchive|url=https://web.archive.org/web/20231216100000/https://books.google.com/books?hl=en&lr=&id=KyxELyTDlsQC&oi=fnd&pg=PA255#v=onepage&q&f=false |date=2023-12-16 }} Pages 255–275 ''in:'' Norris KS (ed.) ''Whales, Dolphins, and Porpoises'', University of California Press.</ref> Fish tails are usually vertical and move from side to side. Cetacean flukes are horizontal and move up and down, because cetacean spines bend the same way as in other mammals.<ref>[http://evolution.berkeley.edu/evolibrary/article/evograms_03 The evolution of whales] {{Webarchive|url=https://web.archive.org/web/20201216005644/https://evolution.berkeley.edu/evolibrary/article/evograms_03 |date=2020-12-16 }} ''University of California Museum''. Retrieved 27 November 2012.</ref><ref>{{cite journal | last1 = Thewissen | first1 = JGM | last2 = Cooper | first2 = LN | last3 = George | first3 = JC | last4 = Bajpai | first4 = S | year = 2009 | title = From Land to Water: the Origin of Whales, Dolphins, and Porpoises | url = http://www.evolbiol.ru/large_files/whales.pdf | journal = Evo Edu Outreach | volume = 2 | issue = 2 | pages = 272–288 | doi = 10.1007/s12052-009-0135-2 | s2cid = 11583496 | doi-access = free | access-date = 2012-11-26 | archive-date = 2020-07-31 | archive-url = https://web.archive.org/web/20200731153046/http://www.evolbiol.ru/large_files/whales.pdf | url-status = live }}</ref>

[[Ichthyosauria|Ichthyosaur]]s are ancient reptiles that resembled dolphins. They first appeared about 245 million years ago and disappeared about 90 million years ago.
<blockquote>
"This sea-going reptile with terrestrial ancestors converged so strongly on fishes that it actually evolved a [[dorsal fin]] and tail in just the right place and with just the right hydrological design. These structures are all the more remarkable because they evolved from nothing — the ancestral terrestrial reptile had no hump on its back or blade on its tail to serve as a precursor."<ref name="Martill, 1993">Martill D.M. (1993). "Soupy Substrates: A Medium for the Exceptional Preservation of Ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany". ''Kaupia – Darmstädter Beiträge zur Naturgeschichte'', '''2''' : 77–97.</ref></blockquote>
The biologist [[Stephen Jay Gould]] said the ichthyosaur was his favorite example of [[convergent evolution]].<ref>Gould, Stephen Jay (1993 [https://archive.org/details/eightlittlepiggi00goul "Bent Out of Shape"] in ''Eight Little Piggies: Reflections in Natural History''. Norton, 179–94. {{ISBN|9780393311396}}.</ref>
<!-- [[Wing]]s are foil type fins used to generate lift on [[flying animal]]s and aircraft, although they are sometimes referred to as fins. The vertical tail fin found on most [[fixed-wing aircraft]] is known as a [[vertical stabilizer]].

;Terminology
There is some degree of overlap and interchangeably between the term ''fin'' and other terms. Most typically, a fin refers to a thin component or appendage attached to a larger body which is submerged in water. Fin-like structure which occur in other contexts are can be referred to by other terms, such as flipper, foil, wing, flap, keel sail or blade.

The term ''wing'' refers to the large fin-like structure that produce lift, particularly in air, such as the main wings of an airplane or bird.

The term ''wing'' often refers to larger fin-like structure that produce lift, particularly in air, such as the main wings of an airplane or bird. Smaller foil-like appendages not used primarily for lift, are still referred to as''fins'', such as ''tail fins''. Birds are said to''flap'' their wings, and the small fin-like appendages to wings that are used to modify their shape are called ''flaps''.. -->

==Robotics==
[[File:RobotFishCharlie.jpg|thumb|210px|right|In the 1990s the [[CIA]] built a robotic catfish called ''Charlie'' to test the [[Feasibility study|feasibility]] of [[unmanned underwater vehicle]]s.]]
{{externalimage
|float=center
|width=200px
|video1=[https://www.youtube.com/watch?v=lEeb72ZJKAk ''Charlie'' the catfish]  – ''CIA video''
|video2=[https://www.youtube.com/watch?v=u8tfES8gImc AquaPenguin] – ''Festo, YouTube''
|video3=[https://www.youtube.com/watch?v=-vT-oidWyXE AquaRay] – ''Festo, YouTube''
|video4=[https://www.youtube.com/watch?v=mKMN-dz8n3k AquaJelly] – ''Festo, YouTube''
|video5=[https://www.youtube.com/watch?v=TKeVVKGEDLc AiraCuda ] – ''Festo, YouTube''}}

The use of fins for [[Aquatic locomotion|the propulsion]] of aquatic animals can be remarkably effective. It has been calculated that some fish can achieve a [[Marine propulsion|propulsive]] efficiency greater than 90%.<ref name=Sfakiotakis>{{cite journal|last1=Sfakiotakis |first1=M |last2=Lane |first2=DM |last3=Davies |first3=JBC |year=1999 |title=Review of Fish Swimming Modes for Aquatic Locomotion |url=http://www.mor-fin.com/Science-related-links_files/http___www.ece.eps.hw.ac.uk_Research_oceans_people_Michael_Sfakiotakis_IEEEJOE_99.pdf |journal=IEEE Journal of Oceanic Engineering |volume=24 |issue= 2|pages=237–252 |doi=10.1109/48.757275 |url-status=usurped |archive-url=https://web.archive.org/web/20131224091124/http://www.mor-fin.com/Science-related-links_files/http___www.ece.eps.hw.ac.uk_Research_oceans_people_Michael_Sfakiotakis_IEEEJOE_99.pdf |archive-date=2013-12-24 |citeseerx=10.1.1.459.8614 |bibcode=1999IJOE...24..237S |s2cid=17226211 }}</ref> Fish can accelerate and maneuver much more effectively than [[boat]]s or [[submarine]], and produce less water disturbance and noise. This has led to [[Biomimicry|biomimetic]] studies of underwater robots which attempt to emulate the locomotion of aquatic animals.<ref>{{cite web|url=http://rjmason.com/ramblings/robotFishMarket.html|author=Richard Mason|title=What is the market for robot fish?|archive-url=https://web.archive.org/web/20090704021443/http://rjmason.com/ramblings/robotFishMarket.html|archive-date=2009-07-04}}</ref> An example is the Robot Tuna built by the [http://fibo.kmutt.ac.th/ Institute of Field Robotics], to analyze and mathematically model [[Fish locomotion|thunniform motion]].<ref>{{cite web|url=http://fibo.kmutt.ac.th/project/eng/current_research/fish.html|publisher=Institute of Field Robotics|title=Fish Robot|author=Witoon Juwarahawong|access-date=2007-10-25 |archive-url = https://web.archive.org/web/20071104081550/http://fibo.kmutt.ac.th/project/eng/current_research/fish.html |archive-date = 2007-11-04}}</ref> In 2005, the [[Sea Life London Aquarium]] displayed three robotic fish created by the computer science department at the [[University of Essex]]. The fish were designed to be autonomous, swimming around and avoiding obstacles like real fish. Their creator claimed that he was trying to combine "the speed of tuna, acceleration of a pike, and the navigating skills of an eel".<ref>{{cite web|url=http://cswww.essex.ac.uk/staff/hhu/HCR-Group.html#Entertainment|publisher=Human Centred Robotics Group at Essex University|title=Robotic fish powered by Gumstix PC and PIC|access-date=2007-10-25|archive-url=https://web.archive.org/web/20110814141015/http://cswww.essex.ac.uk/staff/hhu/HCR-Group.html#Entertainment|archive-date=2011-08-14}}</ref><ref name="cnn">{{Cite web
|url=http://edition.cnn.com/2005/TECH/10/07/spark.fish
|title=Robotic fish make aquarium debut
|work=cnn.com
|publisher=[[CNN]]
|date=10 October 2005
|access-date=12 June 2011
|archive-date=26 November 2020
|archive-url=https://web.archive.org/web/20201126104911/http://edition.cnn.com/2005/TECH/10/07/spark.fish/
}}</ref><ref name="london_times1">{{Cite web
|url=https://www.thetimes.com/travel/destinations/uk-travel/england/london-travel/merlin-entertainments-tops-up-list-of-london-attractions-with-aquarium-buy-6tql7m9knhn
|title=Merlin Entertainments tops up list of London attractions with aquarium buy
|last=Walsh
|first=Dominic
|work=[[The Times]]
|publisher=Times of London
|date=3 May 2008
|access-date=12 June 2011
|archive-date=21 December 2016
|archive-url=https://web.archive.org/web/20161221060004/http://www.thetimes.co.uk/tto/business/industries/leisure/article2172983.ece
|url-status=live
}}</ref>

The ''AquaPenguin'', developed by [[Festo]] of Germany, copies the streamlined shape and propulsion by front flippers of [[penguin]]s.<ref>[http://www.controlengeurope.com/article/24663/For-Festo--Nature-Shows-the-Way.aspx For Festo, Nature Shows the Way] {{Webarchive|url=https://web.archive.org/web/20200928111347/https://www.controlengeurope.com/article/24663/For-Festo--Nature-Shows-the-Way.aspx |date=2020-09-28 }} ''Control Engineering'', 18 May 2009.</ref><ref>[http://www.gizmag.com/bionic-penguins-fly-through-water--and-air/11545/ Bionic penguins fly through water... and air] {{Webarchive|url=https://web.archive.org/web/20160304052906/http://www.gizmag.com/bionic-penguins-fly-through-water--and-air/11545/ |date=2016-03-04 }} ''Gizmag'', 27 April 2009.</ref> Festo also developed ''AquaRay'',<ref>[http://www.technovelgy.com/ct/science-fiction-news.asp?newsnum=2249 Festo AquaRay Robot] {{Webarchive|url=https://web.archive.org/web/20201124125555/http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=2249 |date=2020-11-24 }} ''Technovelgy'', 20 April 2009.</ref> ''AquaJelly''<ref>[http://www.engineeringtv.com/video/The-AquaJelly-Robotic-Jellyfish The AquaJelly Robotic Jellyfish from Festo] {{Webarchive|url=https://web.archive.org/web/20150924000817/http://www.engineeringtv.com/video/The-AquaJelly-Robotic-Jellyfish |date=2015-09-24 }} ''Engineering TV'', 12 July 2012.</ref> and ''AiraCuda'',<ref>[http://www.theengineer.co.uk/in-depth/analysis/lightweight-robots-festos-flying-circus/1009421.article Lightweight robots: Festo's flying circus] {{Webarchive|url=https://web.archive.org/web/20150919071715/http://www.theengineer.co.uk/in-depth/analysis/lightweight-robots-festos-flying-circus/1009421.article |date=2015-09-19 }} ''The Engineer'', 18 July 2011.</ref> respectively emulating the locomotion of manta rays, jellyfish and barracuda.

In 2004, [[Hugh Herr]] at MIT prototyped a [[biomechatronic]] robotic fish with a living [[actuator]] by surgically transplanting muscles from frog legs to the robot and then making the robot swim by pulsing the muscle fibers with electricity.<ref>{{cite journal | last1 = Huge Herr | first1 = D. Robert G | title = A Swimming Robot Actuated by Living Muscle Tissue | journal = Journal of NeuroEngineering and Rehabilitation | volume = 1 | issue = 1| page = 6 | doi = 10.1186/1743-0003-1-6 | pmc=544953 | pmid=15679914 | date=October 2004 | doi-access = free }}</ref><ref>[http://science.howstuffworks.com/biomechatronics4.htm How Biomechatronics Works] {{Webarchive|url=https://web.archive.org/web/20201205000258/http://science.howstuffworks.com/biomechatronics4.htm |date=2020-12-05 }} ''HowStuffWorks''/ Retrieved 22 November 2012.</ref>

Robotic fish offer some research advantages, such as the ability to examine part of a fish design in isolation from the rest, and variance of a single parameter, such as flexibility or direction. Researchers can directly measure forces more easily than in live fish. "Robotic devices also facilitate three-dimensional kinematic studies and correlated hydrodynamic analyses, as the location of the locomotor surface can be known accurately. And, individual components of a natural motion (such as outstroke vs. instroke of a flapping appendage) can be programmed separately, which is certainly difficult to achieve when working with a live animal."<ref>{{cite journal | last1 = Lauder | first1 = G. V. | year = 2011 | title = Swimming hydrodynamics: ten questions and the technical approaches needed to resolve them | url = http://www.people.fas.harvard.edu/~glauder/reprints_unzipped/Lauder.Exp.Fluids.2011.pdf | journal = Experiments in Fluids | volume = 51 | issue = 1 | pages = 23–35 | doi = 10.1007/s00348-009-0765-8 | bibcode = 2011ExFl...51...23L | s2cid = 890431 | access-date = 2012-11-20 | archive-date = 2019-12-06 | archive-url = https://web.archive.org/web/20191206114306/http://www.people.fas.harvard.edu/~glauder/reprints_unzipped/Lauder.Exp.Fluids.2011.pdf | url-status = live }}</ref>

{{clear}}

==See also==
* [[Aquatic locomotion]]
* [[Fin and flipper locomotion]]
* [[Fish locomotion]]
* [[Robot locomotion]]
* [[RoboTuna]]
* [[Sail (submarine)]]
* [[Surfboard fin]]

==References==
{{reflist|33em}}

==Further reading==
{{refbegin|2}}
* {{cite journal | last1 = Blake | first1 = Robert William | year = 2004 | title = Fish functional design and swimming performance | journal = Journal of Fish Biology | volume = 65 | issue = 5| pages = 1193–1222 | doi = 10.1111/j.0022-1112.2004.00568.x | bibcode = 2004JFBio..65.1193B }}
* Blake, Robert William (1983) [https://books.google.com/books?id=M7E8AAAAIAAJ ''Fish Locomotion''] {{Webarchive|url=https://web.archive.org/web/20231216100000/https://books.google.com/books?hl=en&lr=&id=M7E8AAAAIAAJ |date=2023-12-16 }} CUP Archive. {{ISBN|9780521243032}}.
* {{cite journal | last1 = Breder | first1 = CM | year = 1926 | title = The locomotion of fishes | journal = Zoologica | volume = 4 | pages = 159–297 }}
* {{cite journal | last1 = Fish | first1 = FE | last2 = Peacock | first2 = JE | last3 = Rohr | first3 = JJ | year = 2002 | title = Stabilization Mechanism in Swimming Odontocete Cetaceans by Phased Movements | url = http://apps.dtic.mil/dtic/tr/fulltext/u2/a445907.pdf | journal = Marine Mammal Science | volume = 19 | issue = 3 | pages = 515–528 | doi = 10.1111/j.1748-7692.2003.tb01318.x | access-date = 2012-11-23 | archive-date = 2017-02-28 | archive-url = https://web.archive.org/web/20170228064009/http://www.dtic.mil/dtic/tr/fulltext/u2/a445907.pdf | url-status = live }}
* {{cite journal | last1 = Hawkins | first1 = JD | last2 = Sepulveda | first2 = CA | last3 = Graham | first3 = JB | last4 = Dickson | first4 = KA | year = 2003 | title = Swimming performance studies on the eastern Pacific bonito ''Sarda chiliensis'', a close relative of the tunas (family Scombridae) II. Kinematics | journal = The Journal of Experimental Biology | volume = 206 | issue = 16| pages = 2749–2758 | doi=10.1242/jeb.00496| pmid = 12847120 | doi-access = free }}
* {{cite journal | last1 = Lauder | first1 = GV | last2 = Drucker | first2 = EG | year = 2004 | title = Morphology and experimental hydrodynamics of fish fin control surfaces | url = http://www.people.fas.harvard.edu/~glauder/reprints_unzipped/Lauder.Drucker.2004.pdf | journal = Journal of Oceanic Engineering | volume = 29 | issue = 3 | pages = 556–571 | doi = 10.1109/joe.2004.833219 | bibcode = 2004IJOE...29..556L | s2cid = 36207755 | access-date = 2012-12-03 | archive-date = 2020-10-03 | archive-url = https://web.archive.org/web/20201003183836/http://www.people.fas.harvard.edu/~glauder/reprints_unzipped/Lauder.Drucker.2004.pdf | url-status = live }}
* {{cite journal | last1 = Lauder | first1 = GV | last2 = Madden | first2 = PGA | year = 2007 | title = Fish locomotion: kinematics and hydrodynamics of flexible foil-like fins | url = http://www.mor-fin.com/Science-related-links_files/Fish%20locomotion-%20kinematics%20and%20hydrodynamics%20of%20flexible%20foil-like%20fins%20George%20V.%20Lauder%20%C3%86%20Peter%20G.%20A.%20Madden.pdf | journal = Experiments in Fluids | volume = 43 | issue = 5 | pages = 641–653 | doi = 10.1007/s00348-007-0357-4 | bibcode = 2007ExFl...43..641L | s2cid = 4998727 | url-status = usurped | archive-url = https://web.archive.org/web/20121224203303/http://www.mor-fin.com/Science-related-links_files/Fish%20locomotion-%20kinematics%20and%20hydrodynamics%20of%20flexible%20foil-like%20fins%20George%20V.%20Lauder%20%C3%86%20Peter%20G.%20A.%20Madden.pdf | archive-date = 2012-12-24 }}
* {{cite journal | last1 = Standen | first1 = EM | year = 2009 | title = ''Muscle activity and hydrodynamic function of pelvic fins in trout ''(Oncorhynchus mykiss) | journal = The Journal of Experimental Biology | volume = 213 | issue = 5| pages = 831–841 | doi = 10.1242/jeb.033084 | pmid=20154199| doi-access = free }}
* Tangorra JL, CEsposito CJ and Lauder GV (2009) [http://www.people.fas.harvard.edu/~glauder/reprints_unzipped/Tangorra.Esposito.Lauder.IROS2009.pdf "Biorobotic fins for investigations of fish locomotion"] {{Webarchive|url=https://web.archive.org/web/20110401150423/http://www.people.fas.harvard.edu/~glauder/reprints_unzipped/Tangorra.Esposito.Lauder.IROS2009.pdf |date=2011-04-01 }} In: ''Intelligent Robots and Systems'', pages: 2120–2125. E-{{ISBN|978-1-4244-3804-4}}.
* Tu X and Terzopoulos D (1994) [http://kulino.ninehub.com/file.php/1/nhrestore/1/Jurnal_dan_Artikel_Ilmiah/KecerdasanBuatan/sig94.pdf "Artificial fishes: Physics, locomotion, perception, behavior"]{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }} In: ''Proceedings of the 21st annual conference on Computer graphics and interactive techniques'', pages 43–50. {{ISBN|0-89791-667-0}}. {{doi|10.1145/192161.192170}}
* {{cite journal | last1 = Weihs | first1 = Daniel | year = 2002 | title = Stability versus maneuverability in aquatic locomotion | journal = Integrated and Computational Biology | volume = 42 | issue = 1| pages = 127–134 | doi=10.1093/icb/42.1.127| pmid = 21708701 | doi-access = free }}
{{refend}}

==External links==
{{externalimage
|float=center
|width=320px
|video1=[https://www.youtube.com/watch?v=z-XI9MrU1iM Robotic fish to monitor pollution in harbours] ''YouTube''
|video2=[https://www.youtube.com/watch?v=cFxbjy6jvp0 Robotic Fish] ''YouTube''
|video3=[https://www.youtube.com/watch?v=eO9oseiCTdk Robot Fish] ''YouTube'' 
|video4=[https://www.youtube.com/watch?v=S-8WN1bnM9k&feature=fvwrel  Robotic Shark] ''YouTube''
|video5=[https://www.youtube.com/watch?v=SH2ylhHktcg Evolution of the Surfboard Fin ] – ''YouTube'' 
}}
* [http://www.earthlife.net/fish/locomotion.html Locomotion in Fish] ''Earthlife''.
* [http://www.societyofrobots.com/mechanics_FEA.shtml Computational fluid dynamics tutorial] Many examples and images, with references to robotic fish.
* [http://www.zoology.ubc.ca/labs/biomaterials/fishskin.html Fish Skin Research] University of British Columbia.
* [https://www.economist.com/news/2008/11/19/a-fin-tuned-design A fin-tuned design] ''The Economist'', 19 November 2008.

{{fins, limbs and wings}}

[[Category:Animal anatomy]]
[[Category:Watercraft components]]
[[Category:Rocketry]]