Supermodel Petra Nemcova Almost Died in the World's Worst Tsunami. How She Overcame Fear of Water and Healed (Exclusive)

Twenty years after the unprecedented 2004 catastophe, Nemcova shares the painful yet powerful lessons she learned from the disaster that killed her boyfriend

• There was no warning before a tsunami consumed Petra Nemcova's vacation bungalow in Thailand on Dec. 26, 2004, where she was staying with then-boyfriend Simon Atlee

• "I heard Simon screaming my name," she tells PEOPLE in this week's issue, "and it was the last time I heard him"

• Hundreds of thousands of people died, and Nemcova herself barely survived — but in the 20 years since, she has turned tragedy into a source of global philanthropy
  

Petra Nemcova's pelvis shattered in four places when a tidal wave of roiling black water consumed the bungalow in Khao Lak, Thailand, where she and her then-boyfriend, photographer Simon Atlee, were vacationing in 2004.

It was the day after Christmas, and her life was never going to be the same again.

Nemcova started that day — Dec. 26 — by sharing breakfast with Atlee, followed by a peaceful walk on the beach, she tells PEOPLE exclusively in this week's issue. Their holiday had come to an end, and with two hours to spare before they were set to fly home, Nemcova busied herself with some much needed packing while tidying up the bungalow before the couple's departure.

The two were happy and in love, having spent their trip scuba diving, and, unbeknownst to Nemcova at the time, Atlee even had imminent plans to propose.

Their vacation home at the resort faced the swimming pool, which was filled with both relaxing travelers and families entertaining exuberant children. So, when all Nemcova suddenly heard was screaming that morning, she barely had time to catch a glimpse out the window toward the pool before tragedy struck.

For more on Petra Nemcova's account of the 2004 tsunami and other survivor stories, pick up this week's issue of PEOPLE, on newsstands Friday, or subscribe.

"Everything happened in split seconds. I looked up to see frantic movement and people jumping and then in the next second, the wave is crashing into the bungalow and breaking all of the glass windows," she recalls.

Shards of glass sliced Nemcova's skin as the entire bungalow went under. She distinctly remembers Atlee calling out for her.

"I heard Simon screaming my name," she says, "and it was the last time I heard him."

What would become known as the world's worst tsunami and remains the most devastating disaster to tear through Asia was triggered by a 9.1 magnitude earthquake off the coast of Indonesia.

The subsequent series of waves — some reaching reported heights of 150 feet — decimated the region, affecting at least 12 countries and killing an estimated 230,000 people, including Atlee, whose body wasn't recovered until months later. Nemcova barely survived.

Scientists were stunned at the scale of the horror: Nothing like this had happened in modern history, and there had been no warning for the people at the water's edge.

Related: Survivors Remember World's Deadliest Tsunami, Which Killed Over 225,000: 'Everybody Lost Somebody' (Exclusive)

"At some point I couldn't breathe anymore. And I thought, 'That's it.' That's my last moment. And I let go. And actually, it was the most blissful moment of my life," Nemcova remembers now, describing how she made peace with her own death.

"And then, by some miracle, I was able to see sky again."

Nemcova ultimately grabbed the large leaves of a palm tree, where she clung for "an incredibly long eight hours."

The supermodel couldn't move and couldn't feel her legs. All she was conscious of was the excruciating physical pain of her shattered pelvis — and the emotional toll of what was happening around her. Children's wails filled the air, until, one by one, their deafening silence grew much louder.

“Half an hour later, I couldn't hear them anymore. And that meant that they couldn't hold on. I couldn’t swim out [to them] because I was trapped by debris,” Nemcova says. “That day, I couldn’t help. I had no choice.”

Now, 20 years later, Nemcova is looking back at the "many lessons" she learned from the disaster. She turned personal tragedy into action with her worldwide Happy Hearts Fund, which she founded in 2005 with the aim of supporting children who endure these disasters by rebuilding safer schools in the affected areas.

“Hearing children screaming for help and not being able to help them, that leaves such a powerful mark," she says. "Today and every day, I have a choice to help.”

Nemcova's organization has since grown into the nonprofit All Hands and Hearts, unique in their ability to help global communities as they arrive on site early and stay late to help rebuild schools and homes in a disaster-resilient way.

"You are helping others to rebuild their lives, but many times your life also gets, in a way, rebuilt,” Nemcova says of the volunteer work in more than 28 countries globally. “You find a purpose.”

She says her life now is one full of just that: purpose and joy.

She married entrepreneur Benjamin Larretche in 2019 and together they share 5-year-old son, Bohdi. They reside in Miami (by the water, Nemcova notes) where she still practices the three things that she says helped her heal so quickly, all those years ago.

"My meditation and energy work, grieving and gratitude practice and then just focusing on positivity," she explains. "The doctors said that it takes many people with the same injuries [I had] two years to recover. I healed in four months."

The first moment she was able, in the spring of 2005, Nemcova traveled back to Thailand to honor Atlee and the other victims and to thank the locals and volunteers. She also chose to face the waves again by scuba diving — the same activity she and Atlee had enjoyed together just days before catastrophe.

"I went under the water and I was panicking," she says. "My heart was going so fast and I just couldn't even breathe properly, but it's very important not to live in a life of any fear. That's why I did it."

Admittedly, Nemcova says, it took her a few years before "the sounds of palm leaves crashing onto the roof of a hotel or a bungalow" didn't send her body into a full panic, but she worked hard to address her fear head-on.

"And then it lost power over me. If you appreciate the gift of air, if you appreciate the ability to move your legs, everything else is much richer. Your life is happier," she says. "You’re living instead of just surviving."