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Doug Niblack was trying to catch another wave before going to work, when his longboard hit something hard 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, a tail thrashing behind him and water churning all around. It was then that he realized he was standing on the back of a great white shark .

"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."

Jake Marks, an off-duty Coast Guard member who was nearby, 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."

In six years of surfing, Niblack, who grew up in Yelm, Wash., has seen sharks in the water, but never so close.

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.

Collier 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, he said, and when the shark began swimming out to sea, she jumped off.

Niblack says this won't stop him from surfing in the area.

"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."

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