SOLANA BEACH, Calif. -- Shortly after sunrise Saturday, a lone fisherman stood on the beach near where a swimmer was killed by a shark a day earlier.

On the bluff above, authorities kept watch. They said they expected to see people heading into the Pacific to escape summery temperatures even though beaches remain closed from north San Diego up to Carlsbad.

"The closure is on advisory basis," said David Ott, Solano Beach's public safety director. "We're not going to make any arrests or anything," if they spot people going into the water, Ott said, "but we'll go talk to them."

Helicopters searching for signs of the shark that killed triathlete David Martin on Friday will continue scanning the coastline Saturday, said Solana Beach Lifeguard Capt. Craig Miller.

The beaches will be patrolled throughout the weekend, according to city and county officials.

Martin, 66, died on the beach Friday morning after a shark, presumed to be a great white, lifted him out of the water with his legs in its jaws, leaving deep lacerations and shredding Martin's black wetsuit.

Martin, a retired veterinarian, was the first shark fatality in San Diego County since 1994. Prior to that, the last known fatal attack in the area was in 1959.

Even die-hards said word of the attack gave them pause.

"I just got the chills," said Tom Halmos, 36, a regular surfer who biked down to the cove after the attack. "I'm definitely going to go back out but I think the heart rate will be up the first time I do, that's for sure."

Halmos said he planned to stay on dry land for at least the next few days.

"There will be a million beautiful weekends -- what's one less?" he asked.

Experts said the likelihood of finding the shark that attacked Martin was slim.

Sharks are rare in Southern California, though female great white sharks sometimes come south from their usual territory in the cooler waters of the central and northern coast to pup. Few make the mistake of attacking humans instead of seals or sea lions, their usual prey.

"It's just very bad luck for that one man," said Richard Rosenblatt, a professor emeritus of marine biology at the Scripps Institution of Oceanography in San Diego.

Rosenblatt said he believed the bite pattern on Martin's legs indicated the shark was almost certainly a great white that may have been 12 feet to 17 feet long. The sharks, the largest ocean predators, can weigh up to 5,000 pounds, according to National Geographic.

The attack was unusual because it took place over a sandy bottom, Rosenblatt said. Sharks typically attack over rocks, which provide better camouflage.

Solana Beach is 14 miles northwest of San Diego.

Earlier this year, stories of shark sightings swept the coast from San Diego County north through Orange and Los Angeles counties, the Los Angeles Times reported in late March.

The last fatal shark attack in California, according to data from the state Department of Fish and Game, took place on Aug. 15, 2004, off the coast of Mendocino County. The victim was a man diving for shellfish with a friend. On Aug. 19, 2003, a woman swimmer was killed by a great white at Avila Beach in San Luis Obispo County on the central California coast.

Overall, shark attacks are extremely rare. There were 71 reported worldwide last year, up from 63 in 2006. Only one attack, in the South Pacific, was fatal, according to the University of Florida.