A 47-foot stern trawler had started taking on water, sending its two-man crew into the water, one in a life ring and one wearing a life jacket, Kennedy said.
A Coast Guard smallboat crew was able to reach the man in the life ring and pull him aboard.
The boater was taken to shore where paramedics transported him to Marin General Hospital. He was treated for mild hypothermia and shock, Kennedy said.
A search was launched for the second boater. Coast Guard crews used a helicopter, a smallboat and an 87-foot patrol boat to search more than 44 square miles of ocean off of San Francisco and San Mateo counties over eight and a half hours, Kennedy said.
The man was not found and the search was called off just after midnight this morning, Kennedy said.
The Coast Guard received a report that San Francisco police had found a life jacket that washed ashore on Ocean Beach near Lincoln Way, Kennedy said. The life jacket matched the description of that being worn by the missing boater.
The victim’s name is being withheld until his relatives can be notified.
The Coast Guard is asking boaters to avoid going to sea in the next few days unless absolutely necessary, Kennedy said. Forecasts include sunny skies but rough seas and wind gusts between 35 and 45 mph.
All mariners should check weather conditions before setting sail and file a boat plan with someone on shore that includes a destination and approximate return time.
More information on boating safety can be found at www.uscgboating.org.