One man died and another remained missing late Monday after three boaters from the Sacramento area fishing off Tomales Point capsized earlier in the day, authorities said.

A third man was found alive but suffering from hypothermia on the rocks off Tomales Point after an uninvolved boater found the body of a man floating in the water around 9:40 a.m., fire officials said.

That grim discovery set in motion a daylong search in dense fog that included participants from numerous agencies combing the area by land, air and water as the toll of the accident was revealed.

At first, authorities knew only that they had the single victim, the body found in the water. The Roseville man’s name had not been released by Monday night.

A short time later, a U.S. Coast Guard helicopter crew flying with limited visibility managed to spot an overturned boat near Tomales Point, fire officials said.

Marin County Fire Dept. rescuers, including swimmers and Jet Ski operators, were investigating the boat when they spotted the survivor on some nearby rocks, Battalion Chief Bill Roberts said.

Rescue swimmers helped the survivor get into position to be picked up by the Coast Guard helicopter, which brought him back to Lawson’s Landing for a trip to Santa Rosa Memorial Hospital by ambulance.

The survivor told rescuers that the trio had launched from a location inside Tomales Bay around 7:30 a.m. in an aluminum runabout about 18 feet long. They hit a wave near the mouth of the bay that capsized the boat, fire personnel said.

Authorities said it appeared none of the three had been wearing life vests, though vests were found floating in the water.

The survivor, whose name was not available, told Bodega Bay Fire paramedic Marco Barros that he last saw his companions in the water before a wave separated them. He then treaded water for possibly two hours or more before reaching the rocks.

Barros said the water, usually around 55 degrees, was about 60 degrees Monday, apparently aiding the man’s survival.

The missing man — reportedly a dentist out of Roseville and father of five — remained unaccounted for late Monday.

The Coast Guard grounded its helicopter in the afternoon because of heavy fog, but a shoreline and water search continued into darkness before they were suspended.

You can reach Staff Writer Mary Callahan at 521-5249 or mary.callahan@pressdemocrat.com, on Twitter @MaryCallahanB., or Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.

EDITOR'S NOTE: An earlier version of this story said the boat launched from Lawson's Landing, citing an account from one of the survivors. Public safety personnel are not certain yet where the boat was launched from.