An Oregon man surfed on more than just his board Monday - he actually stood atop a thrashing Great White shark for several terrifying seconds.

Doug Niblack was surfing off the coast of Seaside, Ore., when his board hit what he initially thought was a rock. But when he looked down, he saw a dorsal fin and soon realized he was directly on top of the world's most fearsome shark. Then, the beast's tail began thrashing and Niblack jumped off and paddled to shore.

"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 officer who was nearby, said he saw Niblack suddenly standing up, with water churning around him. Although he didn't see the shark, he did see 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."

Ralph Collier, president of the Shark Research Committee in Canoga Park, Calif., and director of the Global Shark Attack File in Princeton, N.J., told the AP such encounters are extremely rare, but not unprecedented.

Niblack said he was standing on the shark for as long as four seconds before it swam away, at first pulling his surfboard, which was tethered to his ankle.

"I'm just screaming bloody murder," he said. "I'm just yelling, 'Shark!' I thought for sure I was gone.

"There was a moment there when everything was going on, I just kind of made my peace," he added. "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.'"