Smashed by a killer tsunami, supermodel Petra Nemcova (search) says she felt a tree crush the bones in her pelvis, then heard the final anguished cries of her boyfriend as he was swept out to sea.

Revealing her agony in a dramatic, interview with ABC's Diane Sawyer (search), the 25-year-old cover girl says her pelvis was broken "many times. I was screaming at the top of my lungs."

Writhing in pain, Nemcova suffered an even deeper anguish. She heard boyfriend Simon Atlee (search) scream, "Petra, Petra," before he vanished in the surging waves.

As she flailed about in the roiling sea, a second wave unleashed its fury and she found herself gulping foul, black water and thinking she was going to drown.

"You just start swallowing the black water for one time, a second time, and then it was quite peaceful in that moment, because I thought, 'That's it. All right.' And it was just very, very peaceful in a strange way," she says.

But suddenly, the water receded and Nemcova was alive — at least for the moment.

The Czech-born beauty recounts her harrowing brush with death and the heartbreaking loss of Atlee, 33, in an hourlong interview that will air at 10 p.m. Wednesday on a special edition of "Primetime Live."

Revealing new details of her incredible ordeal, she says that as she clung naked to a palm tree for almost eight hours, she saw screaming children being swept away, but couldn't help because she couldn't move her legs.

She copes with the loss of Atlee by talking to him and writing to him in a special diary. She feels his presence around her constantly and believes she is living for both of them.

Nemcova, a Victoria's Secret (search) model and Sports Illustrated (search) swimsuit cover girl who was based in New York, and Atlee, a photographer based in London, had a long-distance relationship for two years.

They were vacationing at the Thai beach resort of Khao Lak (search) when the tsunamis struck Dec. 26, killing 230,000.

The couple were battered by not one, but two, deadly walls of water. The first swept them out of their bungalow through a broken window.

"The water was coming in, coming in, and Simon was just saying, 'Petra, Petra, what's going on?' And it was just such a split second, it just pulled us out of the bungalow," she tells Sawyer.

"People were running away and screaming. It was so surrealistic."

Suddenly, there in the swirling, pounding water was an island of uprooted trees, building rubble and other debris.

Thinking it was solid, Nemcova tried to stand on it. But it wasn't and the cruel current began to suck her under.

"It sucked my legs in," she says. "At that moment, the power of the water was bringing all the fallen trees, all the broken buildings and all the wood. It was such a strong current, you couldn't do anything. You just had to go with it."

Just then, Atlee screamed, "Petra! Petra!"

"It's the last time I saw him," says the heartbroken model. "It was so fast."

As her boyfriend disappeared in the waves, tragedy struck again — a fast-moving tree and other debris hit her, shattering her pelvis.

"My pelvis was broken, so my legs didn't work, but I freed my arms. I tried to pull myself and I could do it a little bit," Nemcova says.

As she tried to cope with the stabbing pain and the inability to use her legs, the second wave struck — submerging her under a huge layer of trash.

It was then she found herself gulping the foul water and thought she was going to drown.

Suddenly, the water receded.

"The water released me and I could go up. And then I was so happy to see the blue sky again. I was able to be up and see the world again," she says.

Nemcova saw the top of a palm tree and tried to grab it, but the current was too swift and she failed.

"Then there was another one," she adds. "I didn't see any more of them, so that was my chance. I just grabbed it."

Nemcova clung to the tree for 71/2 hours. The waves had ripped off her clothing.

Did she know her bones were broken? Sawyer asks.

"Yes, because of the power of the tree and the wood, which is breaking it completely," she says.

Could she feel her pelvis breaking?

"Oh, it was breaking many times. I was just screaming from the top of my lungs. Such a power of the water. My left hip, it was pushing it and breaking it and breaking it and breaking it."

As she clung to the palm, she saw children being swept out to sea and heard their cries for help. But to her lasting regret, she was powerless to do anything.

"There was the hopeless thing that I couldn't go and swim to them, or try to help them, because I couldn't move my legs. I couldn't do anything. After half an hour, you didn't hear the children anymore."

The water began to recede, increasing the pain in her pelvis.

"The more down it went, the more painful it got, because the water was lifting my pelvis and keeping it not so painful, keeping it lifted," she says.

Finally, Nemcova was rescued by a group of Thai men who gave her clothes. She asked one of them for his T-shirt and he gave it to her.

Nemcova was taken to a hospital in Phuket, where she stayed for two weeks. The man in the next bed gave her a necklace with a Buddha that she wears every day.

She has now has returned to her native Czech Republic (search), where she is undergoing rehab daily in Karvina, the gray coal-mining town where her parents live.

Dr. Elton Strauss, chief of orthopedic trauma at Mount Sinai Hospital in New York, says Nemcova broke all six bones in her pelvis.

"She is truly a miracle person," he said. "I do not know how she survived."

Nemcova admits she had great difficulty leaving Thailand because she was certain God would return Atlee to her.

"I was very, you know, hoping and having a big hope," she says. "But when the days go by, you have to realize that he will stay in our hearts all the time for forever."

Tears welling in her eyes, she says that she talks to Atlee and writes to him in a diary.

"I never used to write a diary. But now I'm writing a diary to him," she says. "I think it's not just me, but lots of others, family and friends, can still feel him around. He would love us to be happy and smile."

She adds, "I feel that I lost the person closest to me. And I got second chance to live. So, in a way, I feel that I live for both of us."

Nemcova remembers sadly that Atlee loved life and laughter.

"His favorite saying was, 'A day without laughter is a day wasted.' He was so kind and so respectful for people," she recalls. "He loved people. He loved life."

And he was a romantic.

For their first anniversary, he gave her a little book. On each page was a moment they shared together or a lovely message of the things he loved about her. No day goes by without her thinking about Atlee or the tragedy that took him from her.

What was the hardest part of the ordeal?

"One of the hardest things was not knowing if Simon's still somewhere. And needs help. And I couldn't go anywhere. You feel very hopeless, because you don't know [if] there is a chance he needs help."

Nemcova is noncommittal about whether she will return to modeling, saying, "I live day by day."

And she still has nightmares about the tsunami — "water rolling and rolling, and when you close your eyes, just water."

Despite the enormous death toll and the personal tragedy that befell her, she still sees some good in the disaster.

"It brought families together. It brought countries together," she says. "It brought the whole world together for a moment."

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