He has appeared in almost four dozen films in the past 19 years, tackling roles as a heroin addict, a singing French poet, a Jedi master, and a love-struck fisheries scientist. But Ewan McGregor never played a father until starring in "The Impossible," a stirring adventure based on the experiences of a vacationing family separated and imperiled by the Indian Ocean tsunami of 2004.

"Partly it's a matter of what gets put in front of you," McGregor said in an interview following the film's Toronto International Film Festival premiere in September. "Partly it's luck. But I am inspired by good writing. This script moved me to tears. There are some lines in here where the boy sees his mum injured and says, 'I can't see you like this.' Stopped me in my tracks, that line. Devastating. At the end, when they find all the children, I had to put the script down," he said.

McGregor, who lives in Los Angeles with his wife and children, didn't understand at the time that Sergio Sanchez's screenplay was based on a real family's experience. "Then, of course, you realize that these are lines that the family remembered saying, remembered hearing. It's mostly true, 95 percent of it, based on their recollections."

To foster a family feeling with the young actors, McGregor and Watts "hung out and rented films together" with them. "So quickly, we became close and comfortable together. I had three daughters at the time, now I've got four, and here I had three great boys, you know? I liked the relationship with them, that they were in my arms between takes, all over me, sitting on my head and my shoulders. That's part of what drew me, the chance to explore that part of my life. I've been a dad for 16 years, and I've never really explored it in my work. This whole movie is about this unique love we have for our children, this bond we don't have with other people."

The physical demands of the 16-week shoot in Thailand were less than "the emotional rigors of putting yourself into that frame of mind every day with the young kids. That was difficult. I was always the one there before the cameras turned, saying, 'OK, now we're really sad. Really depressed. Come on, you're not sad enough.' After four months of that, they were like, 'What a bummer this guy is, what a downer!'"

It was a different story for co-star Naomi Watts, who spent five weeks being tumbled in a huge water tank for the dramatic wave-impact scene. Watts, who nearly drowned at 14, spent as much time spitting out water as she did speaking lines.

Although the film's focus is the aftermath of a natural catastrophe, McGregor is "uncomfortable referring to it as a disaster movie," which implies a crass exploitation of the tragedy. "We were very careful to be aware of our responsibility to the people who were lost there."

That spirit of restraint led him to talk director Juan Antonio Bayona out of a dramatic close-up. "There was one sort of heroic shot of me coming through a devastated area up a staircase where a building had fallen away. I climbed to the top and called out for my wife as the camera swept across the wasteland and up to a close shot of my face. I told him, 'I think that's just too much of a heroic movie shot,' and it's not in the film, I'm glad to say. The key was that the story had to be leading the moviemaking. If it was ever a cinematic effect leading the story, that was the wrong way 'round."

Colin Covert • 612-673-7186