Open water swimming involves competition in natural bodies of water such as lakes, rivers, bays, or oceans rather than a pool. The distances range from 5 km to marathon swims of 25 km or greater.
Open water introduces variables such as currents, waves, water temperature, and visibility, which make it difficult for athletes to pace themselves, navigate, and draft. Mass starts may be chaotic, so a favorable position on the start line is desirable. Swimmers train for sighting—temporarily lifting the head to spot the buoys—and making stroke adjustments for rough water. Open-water racing is prevalent in triathlons and dedicated marathon swimming competitions that adhere to FINA regulations.
