Rescuers continue search for three people after boat sank in San Francisco Bay

A San Francisco Fire Department vessel passes the city skyline while searching for missing victims after a boat accident near Alcatraz Island off San Francisco (Noah Berger/AP)

Rescuers were still searching for three people missing after a boat involved in a memorial service sank in the cold waters and strong currents of San Francisco Bay near Alcatraz Island, authorities said Wednesday.

One person was plucked from the water by rescue crews but later died, and 16 people were saved after the vessel got into trouble on Tuesday afternoon. A dog on board also died.

Three people are still missing after a boat capsized in the waters of San Francisco Bay (Noah Berger/AP)

A captain of another boat who rushed to help said the waves were choppy at the time.

Videos of the scene Tuesday showed boats deployed to help people who had been on the vessel, which was largely submerged with objects floating nearby.

The vessel’s motor was still running and leaking fuel when rescuers arrived, San Francisco Fire Chief Dean Crispen said.

“Our understanding was there was some kind of memorial service that they were engaging in,” Mr Crispen said.

“They were hit by a wave or took on water, and the boat capsized.”

A department spokesperson, Lt Mariano Elias, described it as a 50-foot (15-meter) multi-level cabin cruiser.

Some 16 people were rescued after the vessel got into trouble (Noah Berger/AP)

Fire department boats “are still searching now,” Lt Elias told The Associated Press.

By Tuesday evening, authorities had been searching in the open ocean on the western side of the Golden Gate Bridge.

The efforts have involved divers, helicopters and vessels.

In July, the average temperature of the bay at 7am is around 59F (15C), according to the Pacific Open Water Swim Company. The temperature is cold but not life-threatening.

All the people rescued on Tuesday were taken to the Gashouse Cove Marina in San Francisco.

A yellow tarp could be seen covering a body on a dock.

A helicopter flies past the Golden Gate Bridge while searching for missing victims after a boat accident near Alcatraz Island (Noah Berger/AP)

Alcatraz Island was once an infamously inescapable federal prison due to challenging waters that surround it.

Now a tourist destination, it is located about a mile north of San Francisco’s shoreline in an often windy area that attracts sailboats and other recreational vessels.

Lt Elias said the vessel was about 550 meters from Alcatraz and the emergency call came in just after 3.30pm on Tuesday.

Mr Crispen said the vessel was believed to have launched near the St Francis Yacht Club in San Francisco.

A person who answered the phone there said the club did not have any information on what happened.