12/31/2012 10:34 am ET

'The Impossible' Director J.A. Bayona On Making A Film About The 2004 Indian Ocean Tsunami

On Dec. 26, 2004, a massive tsunami caused by an undersea earthquake in the Indian Ocean left more than 230,000 people dead or missing in countries throughout Southeast Asia. The Indian Ocean tsunami, with waves over 90 feet in height, was one of the deadliest natural disasters in modern history.

"The first time we heard the story, it had such a big impact that we suddenly felt the need to do the film, even though we knew that it was a huge challenge," Juan Antonio Bayona, who directed "The Impossible," told HuffPost Entertainment.

The new film tells the story of the tsunami and its aftermath from the point of view of Maria Belon (Naomi Watts), a Spanish doctor who was in Thailand with her husband and three children when the disaster occurred. Belon and her husband (played by Ewan McGregor) survived the deadly waves, but were separated from each other: Maria with the eldest child (Tom Holland, in a standout performance); husband Henry with the two younger siblings. "The Impossible" is based on their true story, and recounts the family's efforts to reunite in the days following Dec. 26, 2004.

"I always tried to keep strong empathy with the story," Bayona, who is often credited as J.A. Bayona, recalled. "I worked a lot with the idea of the point of view only being this family. The truth is the whole family gave us the whole scope of the tsunami. What it was like to be at the hospital. What it was like to be out of the hospital, looking for your family."

As Watts told the Associated Press, keeping the story universal was important to the success of the film.

"It was a great pressure and responsibility to get it right because of what she went through and how much she suffered," Watts said of Belon. "And then on top of her story, it was hundreds of thousands of others."

For Bayona, it was also crucial to make sure the tsunami itself was portrayed with accuracy. To make the audience "feel the reality," as he noted, of the natural disaster.

"It was based on a true story, so we never wanted it to be a visual effects show," the director told HuffPost Entertainment. The resulting recreation combines visual effects with miniatures as well as water tanks, all of which create a heart-racing experience for the viewer -- on a budget that was reportedly a fraction of what effects-driven, natural-disaster movies like "2012" and "The Day After Tomorrow" cost. (Per reports, "The Impossible" was made for $45 million.)

"It's always good to have a limit because it forces you to think about all the ways to get what you want," Bayona said about the budgetary restrictions. "Sometimes you get to an idea that you didn't have at the beginning and, sometimes, that's how you get the best idea. The trick is always to make the audience get lost using lots of different techniques."

One of those techniques is sound, which Bayona utilizes to great effect. (The muffled throbbing of flowing water plays a big part in the early going of the film.) As Bayona said, however, it was Belon herself who cracked the code on what the tsnuami actually sounded like.

"She said she suddenly knew what the sound of the tsunami was," he said. "It was the sound of an plane engine."

Beyond the technical aspects of "The Impossible," it also helps that the film cast actors willing to spend weeks submerged in water. Not that it was easy: According to Bayona, Watts experienced stomach issues after a few days because of all the water she was ingesting, but those health concerns paled in comparison with the emotional toll the film took.

"The truth is, the biggest challenge for her was shooting in the same places [as the tsunami] and portraying Maria," Bayona said. "She's an incredible actress and she loved to portray the dark aspects of life. She likes to get in contact with tragedy. She's especially good in portraying that. That's a blessing as a director. She was a very hungry actress. She was the best. She was not just interested in doing a good performance, she was looking for something more."

"The Impossible" is out in limited release now and opens wide on Jan. 4.

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