Jeffrey Helfer of San Francisco was found floating face down in the water Saturday morning during the first leg of the Camp Pendleton International Triathlon.
An autopsy was conducted Sunday, said Michael Ellano, an investigator with the San Diego County Medical Examiner's office.
Another athlete noticed Helfer about 9 a.m. 30 minutes into the race and summoned lifeguards from Del Mar Beach, who pulled Helfer ashore. Efforts at reviving him were unsuccessful and Helfer was pronounced dead shortly before 9:30 a.m.
Helfer had been wearing a full wetsuit to protect himself from what lifeguards described as colder than usual ocean temperatures.
On May 19, an Ohio man died in the Ironman California Triathlon held on the Marine Corps base. Perry Redina, 45, crashed his bicycle into a guard rail at the bottom of a hill and suffered massive head and neck injuries.
The Ironman event is a separate and more strenuous race than Saturday's triathlon.