Open water swimming is a swimming discipline which takes place in outdoor bodies of water such as open oceans, lakes, and rivers. 

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 has featured 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.

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