Depending on the race and finish structure (over a timing mat on the beach or at a vertical finish pad in the water), transponders (or timing chips) can be worn on swimmer’s ankles or wrists during an open water swim.
Generally speaking, if the finish is done vertically (by running or walking over a timing mat on dryland), then the transponder is worn on the ankles. In this case, only one ankle transponder is used. Conversely, if the finish is performed by reaching up and touching a finish pad in the water (like at the Olympics), then the transponder is worn on the wrists. In this case, two wrist transponders are used on both wrists.
During the 2014 USA Swimming National Open Water Swimming Championships 5 km race, Delise Batiza of Roadrunner Aquatic lost her transponder and came over to the referee’s boat to receive and quickly put on a new one [see below]:
Southern California native, born 1962, is the creator of the WOWSA Awards, Oceans Seven, Openwaterpedia, Citrus Corps, World Open Water Swimming Association, Daily News of Open Water Swimming, Global Open Water Swimming Conference. He is Chief Executive Officer of KAATSU Global and KAATSU Research Institute. Inductee in the International Marathon Swimming Hall of Fame (Honor Swimmer, Class of 2001) and Ice Swimming Hall of Fame (Honor Contributor - Media, Class of 2019), recipient of the International Swimming Hall of Fame's Poseidon Award (2016), International Swimming Hall of Fame's Irving Davids-Captain Roger Wheeler Memorial Award (2010), USA Swimming's Glen S. Hummer Award (2007, 2010) and Harvard University's John B. Imrie Award (1984). Served on the FINA Technical Open Water Swimming Committee and as Technical Delegate with the 2011 Special Olympics World Summer Games, and 9-time USA Swimming coaching staff. Note: WOWSA only recommends products or services used or recommended by the community. WOWSA does not receive compensation for links or products mentioned on this site or in blog posts. If it does, it will be indicated clearly on that specific post. See WOWSA's privacy policy for more information.