Twenty years ago, Petra Nemcova woke up the morning after Christmas and was preparing to leave her vacation in Thailand when disaster struck.

In 2004, Nemcova was 25 years old and vacationing with her boyfriend, fashion photographer Simon Atlee, when a tsunami devastated their bungalow on the Andaman coast.

A magnitude 9.5 earthquake off the coast of Indonesia caused the world’s worst tsunami.

Petra Nemcova recalled the “pain” she still feels 20 years after the devastating tsunami in Thailand. (Getty Images)

Atlee was swept away by the waves and not found for three months, and the young supermodel had to cling to a palm tree for eight hours to survive.

SUPERMODEL PETRA NEMCOVA REMEMBERS “split seconds” before she almost died in the 2004 tsunami

ABC News’ Diane Sawyer interviewed Nemcova ahead of the 20th anniversary of the tragic natural disaster.

The now 45-year-old said the pain of hearing the children’s cries and not being able to help them was still “strong” “every day.”

“It’s always difficult to go back to the moment my life changed.”

—Petra Nemcova

“It’s always difficult to go back to the moment my life changed,” she told Sawyer.

On December 26, 2004, Nemcova and Atlee were in Khao Lak, Thailand, preparing to end their trip when the tsunami struck.

Speaking of relying on a palm tree for survival, Nemcova said: “I fell into this stillness, almost a meditative state, because I knew that if I panicked, I would lose even more energy. And it took all my energy to stay alive.”

Atlee’s body was discovered and identified on March 3, 2004. He was among nearly 230,000 people believed to have died during the tsunami.

Simon Atlee, Petra Nemcova’s boyfriend at the time, did not survive the tsunami. (Photo by George Pimentel/WireImage)

It’s a miracle that Nemcova survived. When she was rescued, her clothing had been torn off and she suffered a fractured pelvis and internal injuries, GMA reported.

The people who saved Nemcova were strangers. They gave her clothes, put her on a mattress and pushed her through rubble to get medical help.

“These people were willing to risk their lives for strangers,” Nemcova said. “And that shows you the best of humanity.”

Petra Nemcova clung to a palm tree to save her life. (Photo by Edward Berthelot/Getty Images)

In November, Nemcova told People: “Everything happened in a split second. I looked up and saw frantic movements and people jumping, and the next second the wave crashed into the bungalow, shattering all the glass windows.”

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Nemcova remembered her final moment with Atlee, when shards of glass cut into her.

“I heard Simon scream my name and it was the last time I heard him.”

The model tried to hold on, but eventually “let go.”

Petra Nemkova and Simon Atlee were packing to leave their vacation in Thailand at the time of the tsunami. (Photo by Michel Dufour/WireImage)

“At some point I couldn’t breathe anymore. And I thought, ‘This is it.’ This is my last moment. And actually it was the happiest moment of my life,” Nemcova explained.

“And then, by a miracle, I was able to see the sky again.”

She couldn’t feel or move her legs at this point as she listened to the children’s screams.

“Half an hour later, I couldn’t hear her anymore,” Nemcova told People. “And that meant they couldn’t hold on. I couldn’t swim out (to them) because I was trapped in the rubble. I couldn’t help that day. I had no choice.”

After surviving, Nemcova set out to give back.

Petra Nemcova founded the Happy Hearts Fund in 2005. (Photo by R. Born/WireImage)

She founded the Happy Hearts Fund in 2005 to rebuild schools in areas affected by natural disasters.

“Hearing children screaming for help and not being able to help them leaves such a strong mark,” Nemcova explained. “Today and every day I have the choice to help.”

Since 2005, the Happy Hearts Fund has evolved into All Hands and Hearts.

According to People, the organization will be on the ground in areas on the verge of a natural disaster to help prepare and rebuild homes and schools.

Petra Nemcova flew back to Thailand in 2005 to honor Simon Atlee. (Photo by Richard Corkery/NY Daily News Archive via Getty Images)

Nemcova traveled back to Thailand in 2005 to honor Atlee. The supermodel also decided to face her fear of the water with a scuba dive during the trip.

“I went under the water and panicked,” Nemcova recalled of the outlet. “My heart was beating so fast and I just couldn’t even breathe properly, but it’s very important not to live a life full of fear. That’s why I did it.”

She admitted that it took a few years before “the sound of palm leaves crashing onto the roof of a hotel or a bungalow” didn’t revive her memories.

“And then it lost power over me,” Nemcova explained. “If you value the gift of air, if you value the ability to move your legs, everything else is much richer. Your life is happier. They live instead of just surviving.”

Petra Nemcova will light candles in honor of the dead on December 26th. (Photo by Jim Spellman/WireImage)

On December 26, Nemcova told ABC News that she would be with All Hands and Hearts volunteers and light candles to remember the victims of the 2004 natural disaster.

“We will invite everyone to light a candle with us to bring more light into the world,” she said.

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All Hands and Hearts volunteers include Atlee’s family.

In 2019, Nemcova married entrepreneur Benjamin Larretche and the couple has a son together, Bodhi.

Petra Nemcova married Benjamina Larretche in 2019. (Photo by Gisela Schober/Getty Images)

“I have a son and a wonderful husband, and there are so many blessings to be grateful for,” she said, noting that Atlee’s family has been nothing but kind and loving to her since the disaster.

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“I was lucky because I met my other twin flame…Ben is my twin flame and he’s an incredible soul and I just feel so lucky because I didn’t know it was going to happen,” Nemcova Sawyer said.