With its lean script, clever construction and arresting cinematography, this crass-on-paper bikini movie turns out to be a minor masterpiece.

So much of our best trash ends up in the ocean. Jaume Collet-Serra, the Spanish film-maker whose shimmering, cool approach made the dopey horror flick Orphan something of a must-see, serves up a minor, silly masterpiece with The Shallows. Without an ounce of body fat on its script, the timing for this refreshing splash couldn’t be better, coming as it does during a deadening summer of flabby sequels. For a slick 87 minutes, The Shallows delivers on its promise: Blake Lively, in a bikini, fighting a shark.

If you haven’t already opened a new browser to immediately buy yourself a ticket, I’ll continue. Nancy (Lively), photographed in a golden haze, bums a lift from an unseen Mexican resort to a “secret” beach. Her travelling companion has stayed behind, having quaffed demasiado tequila the night before. The beach is off the beaten path, but Nancy has a number of pictures dated 1991 of her equally athletic-looking mother at the very same spot.

“Mom’s beach?” Nancy’s little sister asks via a FaceTime chat, a cleverly shot but mercilessly short bit of exposition. As if the film needs to fulfil some sort of government-mandated backstory requirement in order to register as a legal motion picture, Nancy’s touch-base with home informs us that she is a medical school dropout struggling with the recent death of her mother. Home is Galveston, Texas, which means she can be both a heartland of ’Murica sweetheart as well as a demon on a surfboard. The almost-a-doctor bit means we’ll buy it when she tears at her wetsuit to create a tourniquet or uses her necklace as a suture.
That’s needed because there’s something more treacherous than sick wipeouts or sharp coral in these waters: a giant, hungry shark. But before the nasty beast shows its teeth, we get ample footage of Nancy on cloud nine, hanging 10, in this quiet cove. When two nice locals say adios for the night, she stays behind to catch a few more waves. The remainder of the picture is of her figuring out how to survive when there’s a vicious person-shredder separating her from safety.

After the initial attack (in which cool blue turns to Argento red), Nancy spends most of her time strategising on a rock that just so happens to have a nice, scooped-out middle for her lie in and resemble a wounded Greek siren. Kudos to Collet-Serra and his screenwriter Anthony Jaswinski for figuring out a way for Lively to undergo a series of costume changes, despite the storytelling hurdle of never returning to shore. First she’s got the wetsuit zipped, then she’s got it not-so-zipped, then she’s got one arm torn off like an Amazonian warrior etc. The camera photographs her above the water, under the water, through the water and with her legs wrapped around a dead and bleeding whale. It’s an all-or-nothing performance and the movie doesn’t shy from embracing the very physical nature of the scenario.

But here’s the key thing: the group of jaded and highly intellectual New York critics that made up the audience at my screening went from snickering at the arguably unnecessary early cleavage shots to gasping, cringing and even murmuring “Oh, no!” as our leading lady suffered increasingly ferocious setbacks. You just gotta jump right in, get your head wet and take this movie on its own terms.

The Shallows is a film begging for you to shout back at the screen, and while the premise is ridiculous, it’s anything but dumb. (I choose not to Google whether or not a shark would hover in one area for a day after it has already chomped other humans.) Each step has an internal logic, shot in a clear and visually arresting manner. Collet-Serra has reteamed with cinematographer Flavio Martínez Labiano and they are incapable of giving us a boring setup. There’s also a good bit of humour, thanks to Lively’s scene partner, a wounded seagull, whose deadpan reaction shots recall a feathery Jack Benny.

The big finish had the crowd cheering, and some of that excitement was without irony. The conclusion is even a tiny bit touching, and without forcing the issue too much, as in the multiple Academy Award-winner Gravity. This isn’t to compare Lively’s performance with Sandra Bullock’s, but there are ample similarities between the two films in their exaggerated energy and go-for-broke simplicity. What could have been mere summertime chum is actually one of the more cleverly constructed B-movies in quite some time.

The Shallows is released in the US on 24 June and in the UK on 12 August.