WHEN Naomi Watts met the Spanish woman she plays in her latest film, The Impossible, the two women sat holding hands in silence. Maria Belon and her family were separated during the 2004 Indian Ocean tsunami that killed more than 230,000 people, and the emotions of that day remain raw.

”I can’t imagine what it would be like to live through a tsunami and have that stretch of time not knowing where your other family members are, so it was crucial that I met her,” Watts says.

”We finally got in a room together and it was just the two of us and we just sat in front of each other and held hands and it became a very silent but powerful moment, because everything is very much still on the surface with her, as far as her emotions.”

Watts was last week nominated for an Oscar for her performance in the film, in which she was forced to confront some of her own fears. She spends a good deal of the film in the water, smeared with mud and blood, and dealing with a possibility that most parents don’t want to think about: losing a child.

The mother of two boys, Sasha, 5, and Samuel, 4 (with her partner, actor Liev Schreiber), Watts says she considers herself ”a pretty fearful person”.

”But at work I actually enjoy facing my worst possible nightmares because hopefully I’m going to learn something out of it!”

Her performance in the film demanded that she confront her own fear of drowning, the result of a childhood experience in Bali.

Born in England, Watts lost her father – a sound engineer for Pink Floyd – when she was seven. Four years later, she emigrated to Australia with her mother and elder brother, Ben, and had a stopover in Bali. ”My mother, myself and my brother got swept out in a very, very bad rip, which is apparently famous in Bali and claims a lot of fatalities,” she says. ”It was terrifying. I didn’t really even understand what was going on, only that my mum, who is meant to be the strong person, was panicking, and then you know something bad is happening.

”We got really lucky and eventually found our way back to the sand, but I’ve always had a little bit of fear about the water since then, so the underwater stuff in this film was truly frightening.”

Although much of the film was shot in Thailand on the site of the rebuilt resort where Belon’s family stayed, the water scenes were shot in a tank in Spain. ”They had everything mechanically worked out so it was a safe environment but I would take a big breath and shoot underwater, with the scuba-divers waiting with regulators nearby in case something went wrong, so that was scary,” Watts says. ”There were times I panicked and had to get out of the water, so it was incredibly challenging for me.”

Spanish filmmaker J.A. Bayona cast Watts and Ewan McGregor as English versions of Belon and her husband, Henry. Belon and her eldest son, Lucas, were swept away in the tsunami and separated from Henry and their two younger sons.

Belon, who was a consultant on the film, finally told her story four years after the event, after she was asked by a Spanish radio program to talk for five minutes on the anniversary of the disaster. Five minutes turned into 50, and one of the listeners was Belen Atienza, a producer who decided to turn the story into a film.

”There were many coincidences that took place to get this story told,” the soft-spoken Belon says over breakfast in a Toronto hotel the morning after the film’s premiere at the Toronto Film Festival. ”What are the chances she was listening the only time I told my story?”

Belon is a trained doctor and a soulful woman who introduces me to her husband and sons as she talks about the audience’s reaction of the night before. She’s more nervous doing interviews than reliving the worst day of her life with an audience of strangers.

”The story is finished and we are alive,” Belon says philosophically. ”It’s been tough, but I cannot let myself be weak because many thousands died and nothing happened to us. What I’ve learnt is that your worst nightmare can happen and you can deal with it and live through it. So every time I’m afraid of something … I remind myself it’s just fear.”

Watts’ best actress Oscar nomination for her performance as Belon is her second. She was also nominated for David Lynch’s 2001 film Mulholland Drive. It’s been two decades since she starred alongside friend Nicole Kidman in the John Duigan-directed 1991 Australian film Flirting.

As she gears up for another big year, which will include the release of her highly anticipated performance as Princess Diana in Diana, she reflects on her far-from-overnight success. ”I pretty much floated under the radar or was quietly sinking, maybe, for a good 10 years before Mulholland Drive,” she says, laughing. ”I remember that time and it feels just like yesterday; I’d be driving from one end of town to another just to get pieces of paper for an audition the next day because those pieces of paper couldn’t even be faxed to my house at that time because I didn’t own one! So I really appreciate the great gift of being invited to work with great people and tell stories worth telling.”

Watts has found happiness on a personal level, too, with Schreiber, her co-star in the 2006 period drama The Painted Veil, and their two children. The New York-based family has relocated to Los Angeles while Schreiber shoots his cable TV series Ray Donovan.

Watts describes both of them as ”gypsies”, but says their children are changing that. ”Our oldest, Sasha, started kindergarten recently so now we have to really rethink things,” she says. ”We have four months in LA with Liev’s show, which isn’t too bad, but you just have to make sure you really want to do something, because if you’re taking your family on the road, you want to make sure it’s worth it.”

■ The Impossible opens on Thursday.

The original release of this article first appeared on the website of Hangzhou Night Net.