NORTH SHORE, Hawaii -- The first monster swell of the big wave season is bringing Oahu the biggest waves surfers have seen in six months on Wednesday.

Waimea Bay drew crowds of spectators as the monstrous waves pounded the shoreline.

Ocean Safety and City lifeguards had their hands full all day, but there were no serious injuries.

At sunset, the huge surf sounded like thunder as it pounded the shoreline at Waimea Bay. The monster waves were so strong it split one surfboard in two.

Robin Bond was with his surf buddy, trying to catch a wave.

"He hadn't even caught one yet. He was paddling out and he sits inside and he took one just right on the head," Bond said. "Just got unlucky."

The board's owner was not injured.

Surfers emerging from the ocean were exhausted but exhilarated. They said the surf was spectacular but challenging.

"The current's pulling, so you just have to know hot to get out, when to get in, what it's looking like," surfer Milo Afong said. "You don't want to get caught on this inside wave here and get slammed."

Crowds of spectators stood onshore and lined Kamehameha Highway above Waimea Bay, to take in the breathtaking sight.

Lifeguards periodically warned excited spectators of the dangers of the high surf, as it crept closer to the water's edge.

The city's Ocean Safety Division and lifeguards were prepared. Their watercraft and rescue surfboards lined the shore along with warning signs.

The large and sloppy surf forced organizers to postpone the O'Neill World Cup of Surfing, the second leg of the Vans Triple Crown.

Lifeguards urged everyone, but the most experienced surfers, to stay out of the water.

"It's just that the waves are too big for sunset beach itself," surfer Fielding Benson said.

"It's big surf it's going to break your board and you're going to have to be ready to take a beating if you're going to go out on a day like today," Ocean Safety Division Lt. John Hoogsteden said.

Lifeguards rescued at least one surfer at Waimea Bay. He suffered a dislocated shoulder.

They issued more than 1,000 warnings, but no one was seriously injured.