Lifeguards began searching for the teen Sunday evening, and the U.S. Coast Guard joined in around 7:30 p.m., officials said.
Some of his companions were rescued after they got caught in a rip current, but they told authorities they did not see the missing teen get pulled under, the San Diego Union-Tribune reported.
A Coast Guard patrol boat searched throughout the night and continued into the morning. A Coast Guard MH-60 Jayhawk helicopter crew searched Sunday night and a second helicopter crew was summoned to conduct a first-light search.
Anyone with information about the missing swimmer's whereabouts was asked to call the Coast Guard Sector San Diego's Joint Harbor Operations Center at 619-278-7033.