Open water swimmers keep gel packs in their bathing suits and drink them at intervals during the race. They are also used commonly by marathon runners and cyclists.
"Fran even talked at camp about how many calories he would consume," said Sabala. "He would cut them on the side and roll on his back and down it and swallow it then throw it in the water."
Some flavors contain 20 to 40 milligrams of caffeine. "That's like five cups of coffee in two hours in the 100-degree heat," he said. "No one is talking about that."
Jeff Konin, an athletic trainer and vice chair of orthopedic and sports medicine at University of South Florida, said, "I have tried GU myself."
"But I've not heard of anyone taking that many before," he said. "Anything in larger doses -- even vitamins -- can be toxic to the body."
Doctors say caffeine is generally "pretty safe."
"It's probably not that likely, but certainly a possible factor in the picture," said Morocco. "Caffeine can cause arrhythmias in sensitive individuals."
The more likely cause of death was hyperthermia, which led to heat stroke.
"During physical exertion as the muscles are working, part of the byproducts is heat, like a power plant," said Dr. Ted Benzer, chief of clinical operations in the emergency department and attending physician at Massachusetts General Hospital.
"The challenge is to get rid of the heat and the body doesn't have that many ways to do that," he said. "The human body underwater is not like a fish or a whale. The primary way it releases heat is through evaporative losses like sweating."
Sweat on the surface of the body creates a cooling effect on blood just under the skin. Unlike a dog, humans can't pant to get rid of the heat.
Heat stroke is seen from time to time in marathon runners during hot weather.
"It is an intriguing concern that [Crippen] had major exertion submersed under very hot water," said Benzer. "But this is very unusual -- I have never seen this in all the years I have worked in emergency medicine."
When the body's temperature reaches 106 to 107 degrees, it starts to cause death of tissue and organ failure.
One of the first warning signs is confusion and delirium as the brain begins to dysfunction. If not treated by cooling the body down, it can cause death.
"It's hard to say what happened," said Benzer. "Who knows who was watching and how closely. Basically, he may have become confused and his actions might have been unpredictable. Maybe he started getting heat stroke, was delirious and then drowned."
But doctors say there are other conditions that can cause sudden death in a young athlete -- heart valve problems, an electrolyte imbalance, congenital thickening of the heart muscle, cerebral aneurysms and even undetected arrhythmias like long QT syndrome.
"He could have been kicked in the head or had a neck injury and drowned," said Dr. Eric Coris, associate professor of orthopedics and sports medicine at the University of Southern Florida.
"But the number one thing that kills athletes is cardiac," he said. "You think heart first."
UCLA's Morocco agrees that many of those medical events could have been treated had there been more attention paid to safety.