Beachgoers were greeted with new warning signs along the San Mateo County coast on Thursday morning after a rare shark attack at the famed Mavericks surf spot.

It was the first such attack in the vicinity in three years and, almost incredibly, the victim was unharmed.

Tim West, a 25-year-old veteran surfer, narrowly escaped his Nov. 2 encounter with what was almost certainly a great white shark. West and friend Chris Loeswick were surfing the spot for just the second time this season, enjoying favorable conditions and uncrowded waters.

West was paddling farther out to prepare for an incoming set when he was suddenly upended by an extraordinary force coming at him from below. West says the shark bumped his arm. Aware of what was happening, West said he took several strokes away from the board.

The shark apparently took the board and released it when it failed to produce any blood. West used his leash to pull the board back to him and then paddled back to shore as fast as possible.

A day later West pulled a fragment of a shark tooth from his brand new board.

"I've got all my limbs on me so maybe it's a good luck board," he said. "I know they're out there. I'm not going to wig out about it."

The attack came just two weeks after Megan Halavais was attacked on her surfboard at Salmon Creek Beach, a mile north of Bodega Bay in Sonoma County.

Almost immediately after the attack, adrenaline still coursing through his veins, West called his father. It was his father who told him to alert the harbormaster.

Harbormaster Dan Temko made the decision to put up signs informing the public of the event.

"People should always be aware when they're out in the ocean that it's the shark's home. If you're out there and suddenly find no other marine life around you there's probably good reason for that," Temko said.

Temko said the signs would probably remain in place for at least a week, barring any further shark activity.

Sean Van Sommeran, a veteran shark researcher from the Pelagic Shark Research Foundation, said there have been more shark sightings in Northern California this year than any year since he began his research in 1990.

He estimates the shark that attacked West was between 12 and 14 feet long and weighed about a ton.

"It looks like the shark didn't even close its mouth," Van Sommeran said, examining the tooth in West's board. "It probably pulled out of the attack before it even got there but was already going at such a speed that it still hit you with some force."

Van Sommeran took a blood sample from West's board and hopes that from that they will be able to determine exactly what shark attacked him. Many local sharks have been tagged by researchers. If it sounds a bit too much like a scene from Jaws, fear not, the shark won't be harmed if found.

• Half Moon Bay Review