Swimfins, swim fins, fins or flippers are worn on the foot or leg and made from finlike rubber or plastic, to aid movement through the water in water sports activities such as swimming, bodyboarding, bodysurfing, kneeboarding, riverboarding, and various types of underwater diving.
Scuba divers use fins to move through water efficiently, as human feet being very small provide relatively poor thrust, especially when the diver is carrying equipment that increases hydrodynamic drag. Very long fins and monofins are used by freedivers as a means of underwater propulsion that does not require high frequency leg movement.
Benjamin Franklin made a pair of early swimfins when he was a young boy living in Boston, Massachusetts near the Charles River; they were two thin pieces of wood, about the shape of an art palette, which allowed him to move faster than he usually did in the water.
Modern swimfins are an invention from the Frenchman Louis de Corlieu, capitaine de corvette (Lieutenant Commander) in the French Navy. In 1914 De Corlieu made a practical demonstration of his first prototype for a group of navy officers, Yves le Prieur among them who, years later in 1926, invented an early model of scuba set. De Corlieu left the French Navy in 1924 to fully devote himself to his invention. In April 1933 he registered a patent (number 767013, which in addition to two fins for the feet included two spoon-shaped fins for the hands) and called this equipment propulseurs de natation et de sauvetage (which can be translated literally as "swimming and rescue propulsion device").
After floundering for years, even producing his fins in his own flat in Paris, De Corlieu finally started mass production of his invention in France in 1939. The same year he issued a licence to Owen P. Churchill for mass production in the United States. To sell his fins in the USA Owen Churchill changed the French De Corlieu's name (propulseurs) to "swimfins", which is still the common English name. Churchill presented his fins to the US Navy, which decided to acquire them for its Underwater Demolition Team (UDT). American UDT and British COPP frogmen (COPP: Combined Operations Pilotage Parties) used the "Churchill fins" during all prior underwater deminings, thus enabling in 1944 the Normandy landings. During the years after World War II had ended, De Corlieu spent time and efforts struggling in civil procedures, suing others for patent infringement.
In Britain, Dunlop made frogman's fins for World War II, but after the war saw no market for them in peacetime, and, after the first supply of war-surplus frogman's kit was used up, the British public had no access to swimfins (except for home-made attempts such as gluing marine plywood to plimsolls), until Oscar Gugen began importing swimfins and swimming goggles from France.
In 1948 Luigi Ferraro, collaborating with the Italian diving equipment company Cressi-sub, designed the first full-foot fin, the Rondine, named after the Italian word for swallow. A distinctive feature of Cressi's continuing Rondine full-foot fin line is the embossed outline of the bird on the foot pockets and the blades.
In 1949 Ivor Howitt or a friend of his mailed to the Dunlop Rubber Company for swimfins; Dunlop answered that they had no plans to make swimfins and saw no use for them in peacetime. Howitt made his own swimfins with innertube rubber stretched across a frame of stiff rubber tube.
Types of fins have evolved to address the unique requirements of each community using them. Scuba divers, in particular, need large wide fins to overcome the water resistance caused by their diving equipment; snorkelers need lightweight flexible fins; ocean swimmers, bodysurfers, and lifeguards favor smaller designs that stay on their feet when moving through large surf and that make walking on the beach less awkward. In general there are two main groups of fins; full foot and open heel. Full foot fins fit like a shoe, and are designed to be worn over bare feet. If a larger size is chosen, however, full-foot fins can also be worn over socks and thin-soled booties. They are commonly used for surface swimming, and are in non adjustable sizes. Open heel have a foot pocket with an open heel area, and the fin is held to the foot by springs or straps. They can be worn over boots, and are common in diving. Many companies design fins with the same fin architecture but a choice of heel type. Other, more specific design trends are listed below.
Common types 
Paddle fins 
These are the most basic fins; a pair of simple stiff plastic, composite, or rubber blades that work as extensions of the feet while kicking. Some paddle fins have channels and grooves to improve power and efficiency though it has been shown that the desired effect does not occur. Paddle fins are widely believed to be the most versatile and have improved swimming economy in men. Tests in women showed a more flexible fin to be more economical, most likely due to lower leg power.
Vented fins 
Vented fins were first designed in 1964 by Georges Beuchat and commercialised as Jetfins. The Jetfin tradename and design were sold to Scubapro in the 1970s. This style of fin is strongly favored by technical divers that use a frog kick allowing a high degree of control but sacrifice speed for low oxygen consumption. Vented fins are generally stiff paddle fins that have vents at the base of the foot pocket. The vents are intended to allow for the passage of water during the recovery stroke, but prevent passage during power strokes due to the blade angle, attempting to lessen effort during recovery and improve kick efficiency. A review and study by Pendergast et al in 2003 concluded that vented fins did not improve economy, implying that water does not pass through the vents. There is a risk of objects catching in the vents.
Split fins 
Some swimfins have the end of the blade split. The manufacturers claim that split fins operate similarly to a propeller, by creating lift forces to move the swimmer forwards. The claim is that water flowing toward the center of the fin's "paddle" portion also gains speed as it focuses, creating a "suction" force. A 2003 study by Pendergast et al called this into question by showing that there was no significant change in performance for a particular split fin design when the split was taped over. The technology used in most commercial split fin designs is patented by the industrial design firm Nature's Wing, and is used under license.
Freediving fins 
These are very similar to paddle fins, except they are far longer, and designed to work with slow stiff-legged kicks that claims to conserve energy. The vast majority are made in the "full-foot" design with very rigid footpockets, which serves to reduce weight and maximize power transfer from the leg into the fin. Freediving fins are commonly made of plastic, but are also often made from materials such as fiberglass and carbon fiber.
A monofin is typically used in finswimming and free-diving. It consists of a single surface attached to footpockets for both the free-diver's feet. Monofins can be made of glass fibre or carbon fibre. The diver's muscle power and swimming style, and the type of activity the monofin is used for, determine the choice of size, stiffness, and materials.
Less usual types 
Open and closed heel fins are predominant, but there is a range of fins that have specialised blade attachment architecture. These include (these names are tradenames):
The Mor-Fin Corporation produces "delfins", which are swimfins that end short and to the end is attached a shape like a fish's forked homocercal caudal fin. The entire fin is based on the anatomy of various marine animals.
Force fins 
"Force Fin" is the trademark for fins designed, developed, manufactured and distributed by Bob Evans Designs, Inc. They are distinguished by an open foot pocket, that encloses only the instep, leaving the toes free so the foot can flex.
Flipfins are an open-heel swimfin designed to allow easy walking on land. Its blade and foot part are separate: the blade hinges onto the foot part at each side, roughly on the level of the metatarsal heads, and when swimming is held in line by a clip on the front of the foot part. On land or when wading the blade can be unclipped and hinged vertically so it does not interfere with walking.
Breast stroke fins 
Open heel fins are secured to the foot by a strap which passes around the back of the ankle. These are usually elastic and may be adjustable. Early fins used rubber straps connected to the fin by a wire buckle, and were not readily adjustable. Later versions incorporated swivels, buckles, quick release connectors and adjustable tension, but the increased complexity and decreased reliability, and tendency of the loose strap ends to hook on things triggered a return by some manufacturers and aftermarket accessory manufacturers to simpler systems. These include stainless steel spring straps and bungee straps, which once set up, are not adjustable, and which reduce the number of potential failure points and places where the fin can snag on obstructions like net, line and seaweed. Some heel straps have a loop for better grip with wet hands or gloves.
Divers are initially taught to fin with legs straight, without excess bending of the knee, the action coming from the hips; a leg action with much knee bending like riding a bicycle is inefficient and is a common fault with divers who have not learned properly how to fin swim. Fins with differing characteristics (e.g. stiffness) may be preferred, depending on the application, and divers may have to learn a modified finning style to match.
The upper limit of a diver's fin-kick thrust force using a stationary-swimming ergometer was shown to be 64 newtons (14 lbf). The maximum thrust averaged over 20 seconds against a strain gauge has been measured as high as 192 newtons (43 lbf). Resistive respiratory muscle training improves and maintains endurance fin swimming performance in divers.
See also 
- Human swimming
- PowerSwim, a device somewhat like two pairs of long thin airplane wings fastened to a scuba diver's hips and legs
- Diving equipment
- Scuba equipment
- Pendergast, DR; Mollendorf, J; Logue, C; Samimy, S (2003). "Evaluation of fins used in underwater swimming". Undersea Hyperbaric Medicine (Undersea and Hyperbaric Medical Society) 30 (1): 57–73. PMID 12841609. Retrieved 11 February 2010.
- Pendergast D, Mollendorf J, Zamparo P, Termin A, Bushnell D, Paschke D (2005). "The influence of drag on human locomotion in water". Undersea Hyperb Med 32 (1): 45–57. PMID 15796314. Retrieved 2008-08-25.
- Pendergast DR, Tedesco M, Nawrocki DM, Fisher NM (May 1996). "Energetics of underwater swimming with SCUBA". Med Sci Sports Exerc 28 (5): 573–80. doi:10.1097/00005768-199605000-00006. PMID 9148086. Retrieved 2008-08-25.
- Davis, RH (1955). Deep Diving and Submarine Operations (6th ed.). Tolworth, Surbiton, Surrey: Siebe Gorman & Company Ltd.
- "Benjamin Franklin (USA) 1968 Honor Contributor". International Swimming Hall of Fame. Retrieved 2009-05-29.
- Alain Perrier, 250 réponses aux questions du plongeur curieux, Éditions du Gerfaut, Paris, 2008, ISBN 978-2-35191-033-7 (p.65, in French)
- In the 1950s capitaine de frégate (Commander) Philippe Tailliez still was thinking that De Corlieu conceived his fins for the first time in 1924 (in fact he'd started ten years earlier). See page 14 in Capitaine de frégate PHILIPPE TAILLIEZ, Plongées sans câble, Arthaud, Paris, January 1954, Dépôt légal 1er trimestre 1954 - Édition N° 605 - Impression N° 243 (in French)
- Alain Perrier, 250 réponses aux questions du plongeur curieux, Éditions du Gerfaut, Paris, 2008, ISBN 978-2-35191-033-7 (p.66, in French)
- Historical Diving Society Magazine, issue 47 (summer 2009), pages 12 etseq, ISSN 1368-0390
- McMurray RG (1977). "Competitive efficiencies of conventional and super-swinfin designs". Hum Factors 19: 495–501.
- Zamparo P, Pendergast DR, Termin A, Minetti AE (March 2006). "Economy and efficiency of swimming at the surface with fins of different size and stiffness". Eur. J. Appl. Physiol. 96 (4): 459–70. doi:10.1007/s00421-005-0075-7. PMID 16341874.
- Pendergast DR, Mollendorf J, Logue C, Samimy S (2003). "Underwater fin swimming in women with reference to fin selection". Undersea Hyperb Med 30 (1): 75–85. PMID 12841610. Retrieved 2008-08-25.
- Apollo Sports USA. "Principles of Split Fin Operation". Retrieved 11 February 2010.
- [dead link]
- "Designing Delfins". Morfin Corp. 2009. Retrieved 30 December 2009.[dead link]
- "Force Fin". Retrieved 11 February 2010.
- Evans, Robert B (14 July 1992). "Open-toed wide-blade swim fin". United States Patent Office. Retrieved 15 February 2010.
- Lee, Marc (2009). "Swimming Fins on Legs". Shinfin Pty. Retrieved 11 February 2010.
- "Flipfins". Omega Aquatics. 2008. Retrieved 30 December 2009.
- Video of Flipfins in use entering from beach and underwater and climbing out onto a boat on YouTube
- "Patent US5374210 - Breast-stroke fins - Google Patents". Google.com. Retrieved 2013-05-10.
- Brittain, Colin (2004). "Practical diver training". Let's Dive: Sub-Aqua Association Club Diver Manual (2nd ed.). Wigan, UK: Dive Print. p. 44. ISBN 0-9532904-3-3. Retrieved 11 February 2010.
- Jablonski, J (2001). Doing it Right: The Fundamentals of Better Diving. Global Underwater Explorers. p. 100. ISBN 0-9713267-0-3.
- Yamaguchi H, Shidara F, Naraki N, Mohri M (September 1995). "Maximum sustained fin-kick thrust in underwater swimming". Undersea Hyperb Med 22 (3): 241–8. PMID 7580765. Retrieved 2008-08-25.
- Lindholm P, Wylegala J, Pendergast DR, Lundgren CE (2007). "Resistive respiratory muscle training improves and maintains endurance swimming performance in divers". Undersea Hyperb Med 34 (3): 169–80. PMID 17672173. Retrieved 2008-08-25.
- Media related to Swimfins at Wikimedia Commons
- Swim Fins, A comprehensive site on swimming fins, including technical information on swim training and cardiovascular exercise using fins.