Supermodel Petra Nemcova opens up 20 years after surviving deadly tsunami

In 2004, supermodel Petra Nemcova was on a dream vacation in Thailand with her boyfriend, fashion photographer Simon Atlee, when a tsunami tore through their bungalow.

Atlee was swept away in the chaos as he called out Nemcova’s name. Nemcova, then 25, survived by clinging to a palm tree for nearly eight hours.

ABC News’ Diane Sawyer interviewed Nemcova in the months after the tragedy. Now, 20 years after one of the deadliest natural disasters in modern history, Petra sat down with Sawyer again to reflect on the horrors of that day, and the kindness of strangers that got her out alive.

"It's always difficult to go back in that moment when my life changed," Nemcova told Sawyer in an interview that aired Thursday on "Good Morning America."

Nemcova and Atlee were packing up to leave a resort in Khao Lak on Dec. 26, 2004, when the tsunami hit, sending massive waves crashing into their bungalow.

As water pulled them outside, Nemcova said she managed to grab onto the top of a palm tree, which she clung to for nearly eight hours before being rescued.

"I went into this stillness, into almost like a meditative state, because I knew if I start panicking, you lose more energy," Nemcova said of the time. "And I needed all my energy to keep alive."

As she clung to the tree, Nemcova said she heard the screams of people crying out for help, including young children.

“I couldn't go and, and swim to them or try to help them because I couldn't move my legs,” she told Sawyer in their original 2005 interview.

When Atlee's body was found and formally identified on March 3, 2004, he became one of the nearly 230,000 people believed to have died in the disaster, which also impacted parts of Indonesia, Sri Lanka, India, the Maldives, Myanmar, Somalia and Malaysia.

For Nemcova, it was a miracle of kindness that saved her. When she was found, her clothes had been torn off by the storm and she had suffered a shattered pelvis and internal injuries.

The people who rescued Nemcova were strangers who gave her clothes and placed her on a floating mattress to steer her through the debris toward medical help, she said.

"Those people were ready to risk their lives for strangers," Nemcova said of her rescuers. "And that shows you the best of humanity."

Tune into "Good Morning America" on Friday, Dec. 20, at 7 a.m. EST, for more of Diane Sawyer's interview with Petra Nemcova.