Surfer, 50, Dies While Riding the Waves : Tragedy: The man apparently suffers a heart attack in waters off Pacific Palisades. At Laguna Beach, three swimmers are injured when swept onto coastal rocks.

A 50-year-old surfer died Monday in the waters off Pacific Palisades after he apparently suffered a heart attack while riding the waves, authorities said.

Witnesses summoned lifeguards after spotting the victim about 11:30 a.m., floating motionless in the ocean off the 17300 block of Pacific Coast Highway, south of Sunset Boulevard. The man was still attached to his surfboard by a leash.

Fire officials said the man was believed to have gone into full cardiac arrest while he was surfing on a day when the warm weather brought large holiday crowds to area beaches. The victim’s name was not released at the request of his family.

Also Monday, three young men from Laguna Hills were injured as they swam in rough seas and were swept onto the coastal rocks at Laguna Beach.

Eric Sedwick, 21, and Andrew McIntyre, 20, were taken to South Coast Medical Center and treated for severe cuts and bruises, Orange County Fire Department officials said. McIntyre’s younger brother, Kevin, also was caught in the waves, but his injuries were not as serious and he was treated at the scene.

Sedwick and the older McIntyre, both on vacation from college, had decided to swim from the northwest tip of Three Arch Bay in Laguna Beach to a beach near the southeast point of the bay. But somewhere along the way, “they realized it was rougher than they thought” and decided to return to shore, said Teri Sedwick, Eric’s mother.

The rising tide pushed the three youths toward the rocky cliffs and smashed them into the rocks, authorities said.

A fisherman called 911 with his cellular telephone, and a Costa Mesa Police Department helicopter soon plucked Sedwick and the elder McIntyre from the beach and carried them to a nearby golf course, where they were met by an ambulance.

Meanwhile, in Northern California, waves like the record-breaking swells that took the life of a world-famous surfer last week claimed two victims Monday when an inflatable boat capsized during a pleasure ride in Tomales Bay.

A 10-year-old boy and his 34-year-old mother died and a man was in stable condition at Santa Rosa Kaiser Hospital with mild hypothermia.

Two other men were airlifted off Tomales Point by helicopter as they were trying to hike to safety. They declined medical treatment, saying they were unhurt.

The waves that caused the inflatable boat to capsize were the result of the same storm out of the Gulf of Alaska that has caused 30-foot waves off Half Moon Bay, about 50 miles south. World-renowned surfer Mark Foo, 36, died there Friday when he was knocked into the water and hit on the head by part of his broken surfboard.