A sheriff's helicopter responded to an emergency call from Fort Ross Reef north of the coastal community of Jenner at about 8:45 a.m. Sunday, according to the Sonoma County Sheriff's Department.
A 61-year-old Daly City man had reportedly been abalone diving alone and collapsed in a parking area known as Fort Ross Terrace as he returned from the water to his vehicle.
As crews aboard the helicopter were in flight, information was received regarding another abalone diver in the same vicinity who had gone missing in the ocean.
Millbrae resident Nathan Ng, 48, had been reported missing by his three diving partners who had returned to shore after becoming separated from him during their dive.
The helicopter crew began an aerial search for Ng above the waters of Fort Ross Reef after dropping off a paramedic to treat the collapsed Daly City man.
A second helicopter flew in to transport the unconscious diver to Sutter Medical Center in Santa Rosa. Details regarding his condition were not available this morning.
Teams with the sheriff's department quickly located Ng, who was spotted on a rock several hundred yards offshore, reportedly in danger of rough surf and an incoming tide.
Sheriff's Sgt. Eric Thomson was lowered from the helicopter on a 100-foot rope, and secured Ng in a rescue harness. The two were safely flown to shore.
Ng told his rescuers he was marooned on the rock after he became overly tired and disoriented during his dive, mistaking the direction toward shore and swimming away from it. He did not report any injuries.