Ehlinger, a resident of Austin, Texas, died at about 7:30 a.m. Sunday during the swim portion of the triathlon, according to race officials.
He apparently died of a heart attack, according to a statement released Sunday by race director Bill Burke.
"We have reason to believe the gentleman suffered from a massive cardiac event as he entered the water and began the swim," Burke said.
"Safety is always our top priority in a race like this. Water safety noticed him immediately and initiated CPR while he was in the water and as they transferred him to land," he said.
"The thoughts and prayers of the entire Escape from Alcatraz Triathlon team are with the family and friends of the racer as they mourn his loss," he said.
The death is believed to be the first in the 33-year history of the race, which includes a 1.5-mile swim from Alcatraz Island to San Francisco, then an 18-mile bike race and 8-mile run through the city.