A U.S. Coast Guard helicopter spotted the 8-to-10-foot shark and immediately notified the Stinson Beach lifeguard station.
At the time, the beach was packed and lifeguards limited swimmers to knee-deep water. National Park Service rangers and lifeguards also patrolled the water on jet skis.
There were no other sightings, but the National Park Service said a several-day ban on swimming and surfing is standard following a shark sighting.
Photo Credit: Sharkdiver.com, via Wikimedia Commons