Two abalone divers died over the weekend in separate incidents at popular diving locations along the northern Sonoma Coast, park officials said.

On Sunday, other divers found a 57-year-old Oakland man unresponsive in the water, brought him to shore and administered CPR, but the man could not be revived, Supervising State Park Ranger Jeremy Stinson said.

The divers had noticed an unattended floatation device commonly used by abalone divers in the water off Kolmer Gulch on the northern end of Fort Ross State Park, Stinson said. They decided to dive below the float to see if the diver was OK.

They found the Oakland man on the ocean floor, still wearing his weight belt, Stinson said. They brought him to shore and began CPR. The authorities were somehow notified, including Timber Cove fire and a State Parks lifeguard who was nearby. Emergency responders took over life-saving efforts but could not revive the man. He was pronounced dead at 5:11 p.m.

The man appeared to have been diving alone and it was unclear how long he had been in the water, Stinson said. His name was being withheld until his family was notified.

On Saturday, State Park lifeguards found a 67-year-old San Francisco man floating in the water in Gerstle Cove in Salt Point State Park, Stinson said.

The man's girlfriend last saw him at 9 a.m. when he set out for a morning of diving, Stinson said. She called authorities at about noon when he didn't return.

State Parks lifeguards found the man's floatation device about 75 yards off shore, and soon found the man floating in the water about 50 yards to the south of the float.

The man was brought ashore and pronounced dead at 12:22 p.m., Stinson said.