U.S. open water swimmer Francis `Fran` Crippen, a world championship bronze medallist, died during a Marathon Swimming World Cup 10km event in the United Arab Emirates on Saturday, world governing body FINA said.
Crippen, 26, won a 10km bronze medal at the 2009 world championships in Rome and a 5km bronze at the world open water championships in Canada this year.
"While the causes of this death remain under investigation, FINA and the entire aquatic community address, in this moment of grief, their deepest and sincere condolences to his family, friends and to U.S. Aquatic Sports and the USA Swimming family," FINA said in a statement.
Crippen, who won two U.S. titles in the pool in the 800m freestyle before switching to open water in 2006, died during the last leg of the World Cup event in Fujairah, FINA said.
On his Facebook page, Crippen posted a message on Thursday saying he was "in Dubai for the final World Cup of the season and then off to Italy for vacation!"
Crippen, who was hoping to become the first U.S. medallist in open water swimming at an Olympic Games in 2012, came from a family that is well known in the swimming world.
His oldest sister, Maddy, competed in the Sydney Olympics in 2000 while younger sister Claire was an All-American at the University of Virginia. Another younger sister, Teresa, swims for the University of Florida and the U.S. National team.
"Fran was a champion swimmer but, more importantly, a tremendous person, and he will be remembered for so many extraordinary qualities," USA Swimming said in a statement.
The United States Olympic Committee (USOC) said in a statement it was saddened to learn of Crippen`s death.
"While details of this tragedy are still forthcoming, we shall keep this outstanding young athlete and his family in our thoughts and prayers."