Around 8:40 a.m. the Pillar Point harbormaster responded to a call that someone aboard a 26-foot boat was having a heart attack, Coast Guard Petty Officer Roy Olson said.
Medical personnel responded and pronounced the man dead on the boat, Olson said.
There were three other passengers onboard, according to Olson.
The man's identity is being withheld as authorities investigate the death, according to the San Mateo County coroner's office.
