'The Impossible' (PG-13)

Naomi Watts and Tom Holland in 'The Impossible'.

The jawdropping truth of The Impossible is, of course, that what happens in the film was possible, at least for a Spanish family caught in the South Asia tsunami that killed more than 200,000 people a day after Christmas in 2004.

In Juan Antonio Bayona’s film, based on the true story of Maria Balon, the family’s nationality is shifted to British to account for the casting of Naomi Watts and Ewan McGregor as tourists who check into a Thai hotel with their three young sons for a holiday vacation and end up facing an unthinkable disaster.

The film doesn’t offer much back story; we learn that Henry (McGregor) works in Japan but worries about being laid off, and that Maria (Watts) is a doctor who’s not practicing at the moment to stay home and raise her boys. Like big brothers everywhere, oldest son Lucas (Tom Holland) wants his little brothers to stop pestering him. But we know all we need to know going in. Who they are doesn’t matter; what they will endure, and how they will behave under unthinkable pressure, is what counts.

Their first days in Thailand are idyllic, the stuff of any vacation: beach; pool; dinners under the stars. Then one day, with no warning, a wall of water crashes down on the resort, separating the terrified family. The rest of The Impossible focuses on their efforts to survive, get help — and find each other, alive or dead.

If you’ve read about Balon, there’s no mystery about what will eventually happen, but the very nature of the disaster proves impossible to dismiss even when you know the outcome. The film is best in the scenes immediately after the tsunami hits, when Maria, being swept along by a crushing current of water, spots Lucas nearby and the two scream for each other helplessly as they’re dragged past debris, dead bodies, even a car floating by with a crying child inside. Bayona is restrained here in terms of gore, but his landscape is a realistic vision of a hell we never hope to visit. Besides, imagination proves capable of conjuring the darker sights survivors probably had to endure in the days after escaping destruction.

The Impossible’s pace inevitably slows after the initial rush, once Maria and Lucas find themselves at a refugee hospital (one powerful shot swings out the doors of the makeshift trauma center to reveal the staggering magnitude of the relief effort). Lucas’ story in particular is unnerving, and young Holland gives an outstanding performance of conveying sheer terror one moment and surprising courage the next. If his childish delight when something good finally happens doesn’t bring tears to your eyes, you might want to check for a pulse.

Once the perspective shifts away from Maria and Lucas, though, The Impossible starts to feel a bit stretched and ultimately devolves into a series of near misses, as one character walks down a hallway seconds before another passes by. It’s as if the filmmakers tried to maximize tension to deliver an emotional punch. But there wasn’t any need to manufacture drama. While it may have been changed for the screen, this story of a family’s ordeal is one from which any parent — any person, really — can’t turn away.

Cast: Naomi Watts, Ewan McGregor, Tom Holland.

Director: Juan Antonio Bayona.

Screenwriters: Sergio G. Sanchez, Maria Balon.

Producers: Belen Atienza, Alvaro Augustin, Ghislain Barrois, Enrique Lopez Lavigne.

A Summit Entertainment release. Running time: 114 minutes. Intense realistic disaster sequences, including disturbing injury images and brief nudity. Playing at area theaters.