CAYUCOS, Calif. -- Chris Kelly thought it was a bit odd that a big rock began moving toward him as he surfed near the Cayucos Pier along California's Central Coast. Then he heard people on the shore began yelling -- "Shark! Shark!"

Kelly quickly began paddling to shore as shocked beachgoers watched the Great White begin to circle him.

“My biggest feeling wasn’t fear; it was confusion,” Kelley told the San Luis Obispo Tribune. “It was more like a big rock that wasn’t supposed to be moving.”

Kelly was able to safely get to shore, but the close call raised anxiety of surfers along the coast after earlier attacks in Marina near Monterey and in the waters off Humboldt County.

State Parks officials posted warning signs Friday along the beach south of the Cayucos Pier after several beach-goers confirmed Kelly's

It was the second time in a week that signs were posted to warn would-be swimmers that a shark had been spotted in the waters off Cayucos.

While California's Central and North coasts are home to Great White sharks, the last few months have seen aggressive behavior by the feared predator.

Late in September, Humboldt County surfer Sue Snyder escaped serious injury when a Great White knocked her off her surfboard and chomped on it. The attack left a 16-inch bite and teeth fragments in the board.

"The guys said it bit my board -- that is what knocked me off the board and onto his back," Snyder, a 52-year-old Safeway clerk who has Save the Sharks bumper stickers on her car, told the Santa Rosa Press Democrat. "I was kind of like in a fetal position, with my arms out. I felt his whole body as he swam by me. Then I kicked him and whether he felt it or not, he didn't come back."

Based on the bite marks in Snyder's board, Ralph Collier of the Shark Research Committee in Van Nuys estimated the shark was 14 to 15 feet long and weighed about 3,000 pounds.

"She was lucky," Collier said. "When you look at the capability of what an animal can do in a predatory attack, it could have been very injurious to her."

In August, a Marina man surfing in the waters off Marina State Beach was attacked by a 12-foot white shark and airlifted to the hospital with torso and thigh injuries.

Witnesses said Todd Endris, 24 of Marina, was surfing with a half dozen other people at Marina State Beach when the shark attacked him from behind.

Loren Rex, a California State Parks spokesman, said the victim screamed and started punching the shark while trying to flee.

"Then the shark took him down under the water," he said. "Witnesses saw a lot of thrashing and some blood coming up. Other witnesses saw the shark let him up before biting him one more time."

One witness said the shark was a Great White shark measuring at least 20 feet long.