NORTH SHORE, Hawaii -- The biggest swell of the season so far kicked off the first major surf contest and it drew big crowds to Oahu's North Shore.

Ten- to 15-foot waves pounded the beaches. The sets were inconsistent, but surfers said they were powerful -- strong enough to snap a board.

At Pipeline, the beach was full of spectators and photographers and plenty of surfers were out enjoying the big waves. There was an injury however. A body boarder was struck by a surfboard and sustained head and back injuries. He was treated on the beach by lifeguards and paramedics.

"You know, it's big surf. It's the biggest northwest swell that we've had this season and we're just urging people to use common sense and caution. If they have any questions, go to lifeguards," Ocean Safety Division Lt. John Hoogsteden said.

At Waimea Bay, the sudden sets sent sightseers scrambling from the shore break.

At Haleiwa, the Triple Crown of Surfing kicked off with the Reef Pro meet.

The crowds thrilled vendors and merchants, who have faced slow business during the recent economic slide.

"With the economy I was worried. I was 'How's the T-shirt biz going to be?' It's been the first day. We are busier than ever here so it's a really good sign," T-shirt vendor Jascque Rarick said.

Forecasters at the National Weather Service said the surf should back down on Friday to 8- to 12-feet high.