​Blake Lively going toe-to-toe with a great white might sound more like the next installment of the “Sharknado” franchise than a surprise summer smash.

But somehow, someway, “The Shallows” manages to defy the expectations and provide frightening, largely enjoyable material and the best shark movie since Steven Spielberg scared people out of the water for decades with 1975’s “Jaws.”

The concept is simple. Lively plays Nancy, a woman looking for alone time surfing on a remote Mexican beach who is attacked just before nightfall by a tremendous great white shark. Against all odds, she is able to maneuver herself onto a small rock several hundred yards from shore with the shark lurking in the shallow water.

Describing the film – especially when you say it out loud – sounds like the worst kind of cinema one could imagine. Executing this unlikely hit in a compelling manner is a credit to director Jaume Collet-Serra and Lively as leading lady, because Anthony Jaswinski’s lackluster script just doesn’t work.

Proving once again to be one of Hollywood’s top young actresses, Lively delivers a homerun performance in a film probably undeserving of one. The part is clearly intended to go to an attractive bombshell who can memorize lines. Lively doesn’t write “The Shallows” off the way many potential moviegoers might. 

Her ability to manufacture credible emotion and character development from subpar material is exceptional. There are so many reasons “The Shallows” shouldn’t work as a movie and Lively fixes nearly all of them with an all-or-nothing performance. 

In the script, Nancy makes miracles happen out of sheer willpower and hokey convenience as it’s clear Jaswinski was watching countless episodes of “MacGyver” reruns while penning his screenplay. Though she doesn’t have chewing gum and a paper clip, Nancy is astonishingly able to avoid certain death numerous times and Lively somehow makes all of this reasonably plausible.

There aren’t really co-stars in “The Shallows” as Lively is left out to dry by herself, with the exception of a computer generated shark and a real seagull Nancy dubs “Steven Seagull” that is unable to fly away due to an injured wing. 

One of the disappointments of the film comes in the shark itself. Whether by design or limited budget, “The Shallows” rarely features its ominous, underwater villain and most of the shark attacks occur off camera. When viewers can see the shark, the effect largely works in terrifying moviegoers. Unfortunately, Collet-Serra plays it safe by taking the camera underwater to signal an impending attack and then pulling away seconds before it happens, leaving viewers with only the aftermath.

Aside from this flaw, “The Shallows” is a gorgeous film shot in New South Wales, Australia, which doubles for a picturesque remote beach on the coast of Mexico. The views cinematographer Flavio Martinez Labiano is able to find and develop help to round out the film and give moviegoers something to be in awe of during the film’s frequent slower moments. “The Shallows” also does a terrific job of flawlessly transitioning above and below water as Collet-Serra calls for that particular shot.

Pacing, however, is a huge struggle within “The Shallows,” something nearly unforgivable for a film that lasts just over 80 minutes. The film progresses like ocean waves, building quickly to incredibly high peaks and then dropping viewers down to a monotonous, boring valley where nothing happens until the next wave arrives.

In this way, “The Shallows” firmly establishes itself in a tier below superior survival movies like “Gravity,” “All is Lost” or “The Martian,” films whose slower moments are equally as compelling as the intense action sequences. But for viewers who know what they’re getting into, “The Shallows” is terrific summer popcorn fodder in the same vein as last year’s surprise hit “San Andreas,” right down to the absolutely absurd events in the final 15 minutes of each movie.

With Lively driving the action in picturesque locales, “The Shallows” is definitely worth a shot in theaters for moviegoers willing to turn off their brains for an hour or so and enjoy the ride.