The worst in nature almost always seems to bring out the best in people. So the most memorable things in “The Impossible” are not the storm scenes – terrifying though those are – but a family’s acts of heroism and persistence amid chaos and destruction.

The storm in question is the tsunami that leveled the coast of Thailand (among other places) on the day after Christmas 2004. The family consisted of five Spaniards: Maria Belon (who’s credited with the original story for the movie), her husband and three sons. They’ve been turned into an English-speaking clan from some undefined country in this version to ensure a wider release, though that shouldn’t prevent you from enjoying the picture.

Or is “enjoy” the right word? We see them battered, literally and psychologically, by skyscraping waves. They are separated, endangered first by the lack of health care and then by confusion in the health care bureaucracy. Intense emotions run high for the last 80 percent of the film, most of them brought on by pain and loneliness and fear.

Director Juan Antonio Bayona and screenwriter Sergio Sánchez have pulled off this balancing act between terror and tenderness once before, in “The Orphanage.” (If you haven’t seen that 2007 classic about a haunted home for children, do so ASAP.) The sensitivity and imagination they bring to “The Impossible” elevates it from a high-toned disaster movie to something more thoughtful.

Consider the way Bayona uses sound. From the first rush of an airplane passing overhead, turbulent noises catch us off-guard: Even a whirring blender has menace.

Yet Bayona switches to silence for many of the tsunami scenes. Where we expect to hear water rushing at us like a freight train, Bayona drops Maria into a soundless maelstrom of currents and debris. When the water turns yellow, she looks like an insect trapped in amber. (“Impossible” sets a standard for underwater mayhem, surpassing the excellent work in Clint Eastwood’s “Hereafter.”)

Sanchez’s script includes elements we’d groan at in a Hollywood movie, including a big double coincidence. (If Belon claims it happened, who are we to doubt?) At the same time, he doesn’t make anyone impossibly brave or enduring; these ordinary people do remarkable things for a short time, then collapse.

Naomi Watts’ performance as Maria has been lauded, because it’s the kind that gets awards. The role requires her to weep and howl and rage and go without makeup most of the way. (The beautifying kind, that is; the bruises, scars and blood clots applied by the makeup crew are superb.)

Yet as fine as she and Ewan McGregor are as the parents, Tom Holland stands out as eldest son Lucas, a slightly sullen teen who learns to put other people before himself.

He also learns, if I read the film right, that chance rules the universe. An acquaintance, delayed on his journey to the beach, survives to mourn the wife and child who went swimming. As we root for Maria and Lucas, we’re reminded of thousands of people who did not reunite with loved ones after the deluge, and we recognize the infinitesimal distance separating the lucky and the unlucky.