"This huge wave just pulled us out of the house," Nemcova, 25, told the Daily News last night from her hospital bed in Thailand. "It was so powerful I couldn't get up. I couldn't get out of it."

"People were screaming and kids were screaming all over the place, screaming, 'Help, help.' And after a few minutes, you didn't hear the kids anymore."

Nemcova and her fashion photographer boyfriend Simon Atlee, 33, were spending the holidays in a beachfront bungalow at the Thai resort of Khao Lak when Sunday's catastrophe struck.

"I heard people screaming and I looked out the window and people were jumping out of the way, jumping into the pool," said Nemcova, who lives in New York and London and was on the cover of Sports Illustrated's 2003 swimsuit issue.

"I was screaming, 'On the roof! On the roof!' I tried to go on the roof but I got sucked away," Nemcova said.

Before she and Atlee could react, a wall of water shredded their wooden bungalow and sent them sprawling into a churning sea of debris that swallowed Atlee without a trace.

She kept her head above the floodwaters and was able to grasp a palm tree before she could be swept out to sea - but had to clutch it for eight hours, watching bodies float past in a scene of unimaginable devastation.

"I just tried to survive and tried to think positive," Nemcova said.

She gripped the tree in excruciating pain under the burning tropical sun until rescuers found her at sunset and carried her to an overwhelmed local hospital on a makeshift stretcher.

"I was so broken, I couldn't walk," Nemcova said. "There were so many people with horrible injuries, with blood everywhere. It was like a war movie."

Nemcova was airlifted to an inland hospital, where doctors found she had a broken pelvis and serious internal injuries.

"There might be pieces of bone stuck to my organs," said Nemcova, who was medicated with morphine but still agonized at her boyfriend's disappearance.

"I can't find Simon," she said. "It was horrible. I'm very lucky, but I can't find Simon."

In New York, her sister Olga Nemcova, 23, and friend Jamison Ernest, a fashion designer, knew only that Nemcova and Atlee were vacationing somewhere near the exotic island of Phuket.

Using credit card records, Internet searches and international cell phone calls, they launched a marathon search that eventually tracked down Nemcova in the hospital.

After a tearful conversation yesterday morning, they got back to work trying to arrange medical-evacuation flights to get Nemcova to the U.S., or perhaps her native Czech Republic.

"I'm just happy that she's okay," Olga Nemcova said. "Now we're praying for Simon."

They frantically E-mailed pictures of Atlee to hospitals and rescue organizations in Thailand, hoping someone would recognize the tall, handsome Englishman with the piercing blue eyes.

"Thank God that Petra is alive," Ernest said. "The biggest concern is to find Simon. He vanished without a trace."

Nemcova and Atlee began dating about two years ago, becoming a dashing, witty couple in the international fashion scene. They were comfortable on glamorous beaches: He shot all the pictures for her 2005 calendar, many of them as they waded together in the warm waters off the south of France.

"They were planning on being in Thailand for two or three weeks - just to be there and go scuba diving, relax on the beach, take a break from their schedules," Ernest said.

Nemcova booked the trip as a surprise for Atlee, so his family in England had no way to find him yesterday until they got a grim call from Ernest.

"We know nothing," Atlee's sister Jodi Hansard said from London, where she waited in agony for any word from British officials. "We knew that they were in Thailand, but we didn't even know where they were."