Open water swimming takes place in outdoor bodies of water such as open oceans, lakes, and rivers.
The beginning of the modern age of open water swimming is sometimes taken to be May 3, 1810, when Lord Byron swam several miles to cross the Hellespont (now known as the Dardanelles) from Europe to Asia.
In the first edition of the modern Olympic Games in Athens in 1896, the swimming competition was held in open water. In 2000, the Olympic Games first included a triathlon with a 1500 m swim leg, and in 2008, a 10 km open water swim. The FINA World Aquatics Championships features open water swimming events since 1992. The FINA World Open Water Swimming Championships was held from 2000 to 2010. Since 2007, the FINA 10 km Marathon Swimming World Cup is held in several events around the world.
The activity has grown in popularity in recent years with the publication of bestselling books on "wild swimming" by authors such as Kate Rew and Daniel Start, and Waterlog by Roger Deakin.
Events such as the Midmar Mile in South Africa (attributed to Wayne Ridden), Great Swim in the UK (attributed to Great Swim with idea by Colin Hill), have helped create and grow interest in participation of the sport.
Though most open water races do not require a specific stroke, most competitors employ the front crawl also known as freestyle. The efficiency of this stroke was demonstrated by Gertrude Ederle, who, as the first woman to swim the English Channel, employed it to beat the existing world record by more than 2 hours.