Marin County's Stinson Beach was closed to swimmers and surfers after a great white shark was spotted Sunday night, according to national park officials.
The shark, which was eight to 10 feet long, was seen about 7 p.m. about 125 yards from shore.
"It was by a former lifeguard and fisherman; he knows what he saw, that is why we are confident it was a great white shark," said John Ralph, the lifeguard supervisor at Stinson, which is part of the Golden Gate National Recreation Area.
Ralph said he immediately got people out of the water at Stinson on Sunday night, and then went to the adjacent Sea Drift and Bolinas beaches to let surfers there know about the sighting.
Stinson and Bolinas are both popular surfing spots.
Ralph said the beach was open Monday, but the water beyond waist deep was closed.
"I have a lot of kids today, I let them go knee deep and let them play with their boogie boards," Ralph said. The National Park Service posted warnings at Marin County's Upton's Beach, which is adjacent to Stinson.