Doug Niblack was trying to catch another wave before going to work, when his longboard hit something hard as rock off the Oregon Coast and he suddenly found himself standing on the back of a thrashing great white shark.

Looking down, he could see a dorsal fin in front of his feet as he stood on what he described as 10 feet of back as wide as his surfboard and as black as his own Neoprene wetsuit.

A tail thrashed back and forth and the water churned around him like a depth charge went off.

"It was pretty terrifying just seeing the shape emerge out of nothing and just being under me," he told The Associated Press on Wednesday. "And the fin coming out of the water.It was just like the movies."

The several seconds Niblack spent on the back of the great white Monday off Seaside, Ore., was a rare encounter, though not unprecedented, according to Ralph Collier, president of the Shark Research Committee in Canoga Park, Calif., and director of the Global Shark Attack File in Princeton, N.J.

He said he spoke to a woman who was kayaking off Catalina Island, Calif., in 2008 when a shark slammed her kayak from underneath and sent her flying into the air.

She then landed on the back of the shark, Collier said. "At that point the shark started to swim out to sea, so she jumped off its back," Collier said.

Coast Guard Lt. J.G. Zach Vojtech said officials do not officially log shark encounters, but he had learned about Niblack’s ordeal from an off-duty member who was nearby when he was knocked from his board.

Jake Marks, the Coast Guard member, said he never saw the shark, but witnessed Niblack suddenly standing up, with water churning around him. He said joined Niblack in paddling as fast as he could for shore after seeing a large shape swimming off between them just beneath the surface.

"I have no reason to doubt there was a shark out there," said Marks. "With the damage to his board, the way he was yelling and trembling afterwards — there is no other explanation for that."

Niblack figures he was standing on the shark no more than three or four seconds, when the shark went out from beneath him. The dorsal fin caught his board, dragged him three or four feet by his ankle tether.

"I’m just screaming bloody murder," he said. "I’m just yelling, ‘Shark!’ I thought for sure I was gone." Before it all happened, he had been spending a couple hours surfing at The Cove, a popular north Oregon Coast surfing spot. He was scheduled to go into work waiting tables later that day.

There were about a dozen other people, but most of them went in when the waves started getting big, leaving Niblack with two other guys sitting on their boards about 50 yards from shore. Niblack had paddled out about 20 yards beyond them, when the swell dropped and his board hit something solid.

He kicked down with both feet, trying to stand up so he wouldn’t get thrashed by the next wave, and found himself standing knee deep in water too deep for standing. "When I put my hands down on it, it felt rubbery like Neoprene, like a wetsuit," he said.

"There was a moment there when everything was going on, I just kind of made my peace. I honestly thought I was going to die. Then paddling back in, I was praying the whole time. Like, ‘Don’t let it be following me.’

In six years of surfing, Niblack, who grew up in Yelm, Wash., has seen sharks in the water, but never so close. He was still shaky when he went to work that night, but was better the next night.

He has been waking up from vague dreams of sharks, but is planning to go back out to surf. When he does he will take a waterproof video camera his roommate gave him. He also put a sticker on the bottom of his board to ward off sharks — a shark with a red circle and a slash over it.

"I’ll definitely go back out," he said. "It’s just the surf sucks right now. I’ll wait ’til that gets better, then go back out."