Swells of 10 to 15 feet had lifeguards working overtime on the holiday at Ehukai Beach, Waimea Bay and Haleiwa, where they pulled 15 people from the waters.
Three rescues were made at Makaha and Nanakuli on the Leeward side. No serious injuries were reported.
The Coast Guard and Fire Department searched the North Shore waters off Mokuleia Beach into the late evening after two beach-goers reported that they thought they saw a man drifting toward Kaena Point around 6:18 p.m. Fire Department officials said the report hadn't been confirmed. The Coast Guard suspended their search this morning.
Fire Department Capt. Thomas Roblin said there were no reports of anyone missing and all vehicles in the area were accounted for.
"It could have been some sort of debris" that the witnesses spotted, he said.
A high surf advisory remained in effect today for all north and west shores of the Hawaiian Islands, with waves between 8 and 12 feet expected.
Sunny skies drew throngs of nonsurfers to the beaches as well, and that kept lifeguards busy with megaphones warning the unprepared to stay out of the surf.
"This is the lifeguards' busiest time of the year, without doubt," said acting Capt. Mark Cunningham of the city Ocean Safety and Lifeguard Services Department.
Surf on the Leeward side was in the 4- to 8-foot range but it still packed a punch, Cunningham said. He said swimmers and surfers should be sure to know their limits if they planned to venture into the water today.
The high surf is being generated by a storm about 1,500 miles northwest of Hawaii that is expected to continue into the weekend, said National Weather Service lead forecaster Bob Farrell.