( CNN ) -- Fran Crippen , a star open-water swimmer , was at a competition in the United Arab Emirates when he made a promise to his longtime prep-school coach back in the states . He would call by 5 a.m. Saturday with the outcome and details of the 10-kilometer Marathon Swimming World Cup . Richard Shoulberg , who began coaching Crippen when he was 7 years old , knew something was wrong when the athlete had not called by 5:45 a.m . ET , he told CNN . Indeed , in the UAE , divers were searching for Crippen after he did not finish the race . They found his body two hours later . The loss of Crippen , 26 , hit hard in suburban Philadelphia , where he grew up in a family of swimmers who trained and began competing there . Crippen was on target to achieve his goal of being an Olympian -- a dream cut short . `` We 're all grieving . We 're all in shock , '' Shoulberg said . Doctors determined that severe fatigue was behind Crippen 's sudden death , UAE Swimming Federation Secretary Saeed Al Hamour told CNN Sunday . Earlier , however , the head of the water sports club in Fujairah , Ahmed Ibrahim , said that preliminary tests showed that he suffered a heart attack . The official report released by the UAE Swimming Federation made no mention of a heart attack . `` We do not know , '' Shoulberg said about the cause of death , adding that Crippen was `` fit as a fiddle . '' Crippen died Saturday during the last leg of the Marathon Swimming World Cup in Fujairah , the International Swimming Federation ( FINA ) said in a news release . The cause of death is under investigation , FINA said . In a conversation with Shoulberg 12 hours before the race , Crippen said that the outside temperature was 100 degrees and that the water was 87 degrees . The high temperatures have led to some speculation that it may have contributed to the death . However , Al Hamour denied any reports that Crippen 's death may have been caused by water temperature or cleanliness . `` The competition was monitored and supervised by the International Swimming Federation . All security measures were taken care of as needed , '' Al Hamour said . `` We 've organized so far 14 competitions and championships and never had any death . '' Swimming World magazine reported that Crippen fell unconscious during the event and was found by deep-sea divers two hours later near the race 's final buoy . The U.S. Olympic Committee issued a statement Saturday saying it was `` extremely saddened '' to learn of Crippen 's death . `` We send our condolences and deepest sympathies to the Crippen family as well as to our entire swimming community , '' the USOC statement said . `` While details of this tragedy are still forthcoming , we shall keep this outstanding young athlete and his family in our thoughts and prayers . '' Crippen won bronze in the 10-kilometer event at the 2009 FINA World Championships and was the gold medalist in the same event at the 2007 Pan American games , according to USA Swimming . Crippen , of Conshohocken , Pennsylvania , was inspired to take up swimming at age 6 after watching older sister Maddy Crippen compete in the water . Maddy Crippen was a member of the 2000 U.S. Olympic team , according to USA Swimming . Crippen graduated in 2006 from the University of Virginia where he was twice named Atlantic Coast Conference Swimmer of the Year . He was to be inducted into the athletic hall of fame of his former prep school , the Germantown Academy next month . Instead , he is being remembered as a dedicated swimmer who gave his time to teaching young children how to swim , and introducing high school swimmers to open-water swimming . `` He was an unselfish human being , '' Shoulberg said . Crippen 's body will be handed over to U.S . Swimming Federation authorities on Monday . Shoulberg said he hoped his body would be brought home within 48 to 72 hours . CNN 's Caroline Faraj contributed to this report .
NEW : Coach says swimmer was in great pain . Doctors believe that severe cold was a factor . Fran Crippen , 26 , dies during last leg of 10-kilometer open - water race . He fell unconscious and was found two hours later , a magazine magazine .