It happened off Point Reyes National Seashore in Marin County just west of Abbott's Lagoon.
The Coast Guard stationed in San Francisco received a call just after noon Wednesday from a fishing boat reporting that it had seen a 25-foot open cockpit Bayliner-type boat capsized in the surf 10 miles north of the Point Reyes lighthouse, with four people clinging to the hull.
The Coast Guard sent two boats from Bodega Bay as well as two helicopters, but by the time they arrived on scene, all they saw was debris from the boat in the water. Crews were able to recover two of the accident victims but both were unconscious. Rescuers performed CPR all the way back to Bodega Bay but it was too late and both died.
Marin County fire batallion chief Tim Thompson was among the rescuers.
"By the time we got out there, the Coast Guard had retrieved two of the subjects. CPR was in progress. The Sonoma County Sheriff's helicopter had eyes on the third subject submerged in the surf. We spotted them as well. We were going to try to work with them to retrieve the body as it washed on shore."
Divers are still trying to recover a third body that was seen floating close to the shore. A fourth person has been reported missing and is presumed dead.
Where the boat or its passengers are from remains unknown. Rescuers from Marin County say they have been cross-checking fishing licenses and other identification.
"The two people that were recovered did not have life jackets on and the Coast Guard would like to take this opportunity to remind boaters to carry their life jackets, wear their life jackets when out on the water." Coast Guard Lt. Jeanie Lusk said. "Also, the Coast Guard did not receive a distress call on VHS FM channel 16 and that is the international hailing and distress frequency."
Water conditions off of Point Reyes National Seashore were extremely calm all day Wednesday. Top winds reached 5-10 mph. Rescuers said the seas were not the kind of conditions that one would expect to capsize a boat.
Authorities speculate the boat may have hit something or become caught inside the surf line.