Marathon Swimming is long distance swimming across large bodies of water such as the Great Lakes, the Atlantic Ocean and the English Channel. Marathon swimming is an endurance sport that pits a swimmer not only against other contenders in the race but also against the currents and tides of the water. According to International Swimming Federation rules, swimmers cannot use wet suits as this can artificially increase speed or endurance. Swimmers are accompanied by a nearby boat crew that monitors and advises the competitors.