Ben Carlson, 32, was pulled from the water around 8 p.m. PDT by fellow lifeguards following a frantic, three-hour search, Newport Beach Fire Department Chief Scott Poster said.
Poster said the 15-year department veteran went into the water Sunday to help a struggling swimmer when they were hit by a large wave. Carlson went under water, and the swimmer made it to shore safely. Poster said searchers were hampered by up to 12-foot swells.
"It was just an utter tragedy to lose a man of that caliber in the water today," the chief said, noting that it was the first time a city lifeguard died in the line of duty.
"Ben was a well-respected individual, always a nice guy, always was there to help somebody," Poster said. "He'd give his shirt off his back at anytime."
The National Weather Service had issued a warning Sunday of dangerous rip currents and high surf along Southern California beaches. The weather service said some beaches saw up to 8-feet high surf.
Los Angeles County firefighters rescued a 25-year-old man who was caught in the waves off Rancho Palos Verdes and high tide breached a sand berm in Long Beach.
The lifeguard's death came a day after a 50-year-old long-distance swimmer and former lifeguard was bitten by a shark off Manhattan Beach.
Authorities and witnesses said the 7-foot-long juvenile had been trying to free itself from a fisherman's hook when it lunged at Steven Robles' chest.
The beaches remained open, but police prohibited fishing from the Manhattan Beach pier where the fisherman hooked the shark until Tuesday.