A string of popular beaches along Bogue Banks was closed to swimming and surfing early today by local officials concerned about heavy concentrations of sharks along the shoreline.

But hundreds of vacationers defied the police order, daring the sharks and entering the water anyway.

Officials said water temperatures, which have been above 80 degrees, may be a factor in the sharks' swimming close to shore. The high temperatures have driven out the fish sharks normally feed on, and the sharks have come closer than usual to shore looking for other food.

"The sharks are hungry," said Connell Purvis, director of the state Division of Marine Fisheries at Morehead City.

The sharks sighted include hammerheads, tiger, black-tip and spinner sharks, which normally are not harmful to man. But officials said activity in the water could attract the attention of sharks, and invite an attack if they are feeding.

A surfboard, said Pruvis, "acts as a lure for the sharks." Sharks have followed surfboards to the beach in two instances, he said.

No attacks on humans have been reported, but a shark "took a bite out of a surfboard" in an incident this week near Emerald Isle, Purvis said. Frank Schwartz, a shark specialist with the University of North Carolina's Institute of Marine Science, said another surfer fell off his board onto a shark, but was not injured.

J. M. Tucker II, Atlantic Beach police chief, said the closing affects all the Carteret County beaches from Atlantic Beach to Bogue Inlet, including such beaches as Emeral Isle, Indian Beach and Pine Knoll Shores. He was unable to say how long the beaches would be closed.

No sharks have been spotted at other popular beach areas along the North Carolina or South Carolina coast.

Biologists said sharks in schools of 60 or more and weighing from 50 to 300 pounds were sighted in water as shallow as three feet along the area from Bogue Inlet north to Cape Lookout.

Schwartz called the shark infestation "a once-in-a-blue-moon situation," but said there would be no relief until there is a major change in the weather that would lower ocean temperatures.

The decision to close the beaches was supported by the mayors of nearby towns and other officials of this popular tourist area.

"This isn't a 'Jaws' situation," said Doug Everett, president of the Carteret County Chamber of Commerce. "But we would rather let the visitors and the citizens know the sharks are there."