Fran Crippen ran the New York Marathon last year, and qualified for Boston's. He was an experienced distance swimmer with nary "a speck" of an issue in his medical history, according to his family.

So members of his Conshohocken family and fellow swimmers expressed incredulity Monday after learning that the United Arab Emirates had declared "drowning" as the cause of the aspiring Olympian's death during a 6-mile race on Saturday off that nation's east coast, in extraordinarily warm waters.

USA Swimming, the U.S. competitive swimming governing body, announced Monday that it would conduct its own investigation, independent of a probe by FINA, which staged the World Cup event at al-Fujayrah.

"We are going to go through every avenue to see how this could happen," said his sister, Maddy Crippen, herself a former Olympic swimmer. "There should not be a drowning at a swimming event," she added. "He was at the top of his game."

She added that his body would be flown back to the United States on Thursday, and "we'll have our own medical team examine Fran."

Ironically, Crippen, 26, a former Germantown Academy standout who grew up in Conshohocken and was a member of an elite swimming family - another sister is an all-American at the University of Virginia - was deeply concerned about the safety aspects of open-water competition.

Maddy Crippen said that on Sunday, her brother's girlfriend had forwarded to her a draft memo he had written advocating, among other things, the presence of qualified medical personnel at meets.

"Fran wanted to make sure that we were doing everything right," she said. "He was going to take that cause on himself. He wanted to be the face of open-water swimming."

While marathon open-water racing dates to the ancient Japanese and the Roman Empire, it did not become an Olympic event until 2008.

Experts say the hazards have yet to be fully vetted.

"We have never researched our sport like other sports have," said Steven Munatones, a current member of the FINA open-water technical committee.

Thomas Lurz, the German who won the al-Fujayrah event, said on Sunday that the air and water temperatures were dangerously high. Lurz said the water was at least 86 degrees, though one official said it was 84. Three other swimmers reportedly were hospitalized.

Munatones said no country had set upper thermal limits for water in a sport where competitions are held in the Caribbean, South Pacific, and Florida.

"There is no information on heat exhaustion in the water," said Munatones, who also edits a website devoted to open-water swimming.

Water swamps a key mechanism: sweating. Think of humidity to the nth power. Sweat has to evaporate to export heat from the skin, noted William O. Roberts, a professor at the University of Minnesota Medical School and past president of the American College of Sports Medicine.

The body's ability to cool itself by increasing blood flow to the skin is limited. The body temperature can keep rising if the water is warm enough and the level of exertion high enough, said Todd Trappe, a former collegiate swimmer and a professor of exercise science at Ball State University.

Of further concern: An overheated body means an overheated - and likely underperforming - brain, said Michael F. Bergeron, director of the National Institute for Athletic Health and Performance in Sioux Falls, S.D.

"The athlete is probably the worst person to assess the severity of the situation," Bergeron said. "It's not surprising that an overheated swimmer would keep going until they drown."

But distance swimmers aren't to be confused with waders, said Stephen "Sid" Cassidy, a longtime race coordinator and former head coach of USA open-water swimming. Cassidy said long-distance swimmers have "legendary" mental abilities.

"Open-water swimmers have an incredible mental edge over the day-to-day pool swimmers or recreational swimmers," he said. "It takes so much physical, mental, and emotional preparation to compete in a marathon swim."

There is little room for error in the open ocean, where waves can swallow a swimmer and currents pull them chaotically, with no pool lines to follow and with stinging jellyfish and poor visibility.

Fran Crippen was an experienced competitor. "He loved what he was doing," said his mother, Patricia Crippen. "He loved to train."

He trained regularly at the pool at his alma mater, Germantown Academy, was a volunteer coach, and gave swimming lessons to preschoolers.

On Monday, his signature black kickboard was placed alongside the pool with the requisite coffee cup atop it, school spokeswoman Carla Zighelboim said.

She said the school would have a memorial event Nov. 12 at its annual Hall of Fame banquet. As fate would have it, Crippen had just been elected to the hall.

She added that the school had a moment of silence for him on Monday and made grief counselors available.

"We have a lot of wonderful memories," Patricia Crippen said. "People are saying wonderful things to us, some things we didn't know about."

As guests filed out of her Conshohocken home Monday, she had but one request: "Hug your kids, everybody."