An 18-foot speed boat dropped off more than a dozen people along the shores of North Torrey Pines State Beach, according to law enforcement officers.
Lifeguards received reports of people in the water north of La Jolla around 8 p.m. Sunday.
Seven people swam to shore and were taken into custody because they were believed to be undocumented immigrants, San Diego police said.
This section of San Diego's shoreline has been the destination of several smuggling boats in recent months.
A search for 10 people seen on board a suspected smuggling boat in March turned up empty after suspects were seen jumping out of the boat just after midnight at Torrey Pines State Beach and leaving in a pick-up truck.
The speed boat used in Sunday's incident was anchored about 100 miles off shore. It has been towed to San Diego and will be turned over to the police.