SAN DIEGO — Along a San Diego beach chewed away by winter swells, at least eight people died after the small boats they were in capsized in what the authorities said on Sunday was a human smuggling operation gone awry.

Capt. James Spitler, sector commander of the U.S. Coast Guard in San Diego, said that one boat carrying approximately eight people made it ashore, while the other, carrying an estimated 15 people, overturned in the surf.

James Gartland, the head of the San Diego Fire-Rescue Department’s lifeguard division, called it “one of the worst maritime smuggling tragedies” in recent years.

“Often these boats are poorly maintained and overloaded,” Mr. Gartland said.

San Diego Fire-Rescue Department lifeguards responded to a 911 call around 11:30 p.m. on Saturday, according to a department spokeswoman, Mónica Muñoz.

The caller, a woman speaking Spanish, said she and other passengers of a panga boat, a small fishing vessel, had reached the shores of Black’s Beach, a secluded strip of sand beneath the bluffs of Torrey Pines on the Pacific Ocean.

The caller said that another panga boat had capsized.

By the time lifeguards arrived, their attempts to reach the beach were hampered by high tide and a heavy fog. They found both boats were capsized and inside the shore line. No survivors were found.

Lifeguards found “lifeless bodies and two overturned pangas spread over an area of about 400 yards,” Ms. Muñoz said. “Several life jackets and fuel barrels were also found.”

“Lifeguards pulled victims from knee-deep water and from the waterline up the beach to dry sand,” she added.

Mr. Gartland said he could not confirm any demographic details of the dead or surviving passengers. It was not immediately clear how many people officials believed remained unaccounted for. It was also unclear where the boats were coming from.

Survivors could have taken one of several steep trails up the beachside cliffs, including one that arrives at La Jolla Farms, a wealthy San Diego enclave of gated, multimillion-dollar homes.

Search efforts at Black’s Beach were continuing on Sunday as dozens of surfers in wet suits tackled the waves.

Responders from the Coast Guard and U.S. Border and Customs Protection and lifeguards were working at a site where two boats with outboard motors were perched on the sand, right side up. In both were strewn life jackets, plastic bags and clothing. One boat had the top of its motor smashed.

A series of sandbars and dangerous rip currents make the water around Black’s Beach particularly treacherous, the authorities and local surfers said.

Rescuers have responded to dozens of calls this year involving swimmers, surfers and mariners. At least 23 people have died in smuggling cases in Southern California since 2021, Captain Spitler said.

“Sadly, this tragedy continues and has been happening for quite some time,” he said.

“This is not necessarily people trying to find a better life,” he added. “This is part of a transnational criminal organization network to smuggle people into the United States.”

The swell of the waves on Saturday reached about three feet, not particularly high for Black’s Beach, Mr. Gartland of the fire department’s lifeguard division said.

“Yesterday was a mild day for surf, though that doesn’t mean for the average person it would be a manageable experience going out in the waves,” Brian Pickett, a surfer from La Jolla, said.

“It doesn’t take a giant swell to make Black’s Beach dangerous to the average person,” he added.

Emily Schmall reported from New York, and Sara Clemence reported from San Diego.