THE SHALLOWS may not be deep, but it is about something, and, to boot, smartly ironic. Blake Lively makes her way, as the generically named surfer “Nancy,” a med school student re-evaluating her life, to a secluded Mexican beach. She is solo, as her girlfriend travel companion is laid up from a bender the night before, and has hitched a ride with a local, who berates her for violating the spirit of the excursion with her constant cellphone activity. The director Jaume Collet-Serra envisions the cloud world she inhabits by surrounding her with floating images of her conversations. The whole point of the “secret beach” she’s heading to is to cut off the world and find oneself in the process. You can tell she gets that she ought to disconnect but that it’s easier said than done. At the beach, though, the incompatibility of water and her cellphone decides the matter, and she ventures out, happily disconnected, waving off offers of company from a couple of male surfers.

Before long she is alone in the water, the two guys a far-off sight quaffing beers in a van on the beach. It is a beautiful place, and one gets a sense of that from Collet-Serra’s visual deftness; perhaps Nancy will find, if not peace, then at least a piece of herself. We get some of the adrenalin rush of the wave, as well, but it’s not the excitement of the surf that THE SHALLOWS is about, nor even the unexpected threat that Nancy will endeavor to overcome. It’s that the main impediment to surviving the danger is her inability to connect with anyone who might be able to help her or summon assistance. The moral irony that screenwriter Anthony Jaswinsky gets at is that the interminable state of connectivity we are in these days is both dehumanizing and salutary. It disconnects us from whom we are with at a given time but sustains friendships at a distance, destroys direct experience but enables the lifesaving call. Is it worth killing the unmediated self day-to-day to preserve it in a moment of crisis? Had Nancy been able to take her phone with her, there wouldn’t be a movie, at least not this one, which, as it is uncommonly gripping and well made, adds something to the irony.

It is no secret, and so no spoiler (stop now if you fear such), that the danger she faces is a shark. The turn comes earlier, however, with the marring of the “beauty of nature” with its more complex reality: the carcass of a whale that has floated into the shallows. As it bleeds and decays, it attracts both seagulls (which, for all the affection we have for them, are scavengers, like vultures or crows) and, since Jaws, the quintessential aquatic predator. Moby Dick lies putrefying with no Ahab in sight, as the mindless menace catches Nancy’s scent in the water. It is now wit versus brawn, an intelligent woman, medically trained and water smart, triangulating between three points of safety – a rock that will be submerged at high tide, a bobbing whale, and a buoy. Sorely missing is the connectivity that before her present crisis had stripped her soul but that now could save her.

There is an injured seagull who keeps her company and on whom she will, if he will tolerate her touch, exercise her medical skills. She will use them on herself as well. There are myriad ingenious efforts at communication. She survives, or she does not. Lively, even more than the surefooted filmmaking, makes the movie. Make no mistake how smart she is when she acts. She has yet, in several films, to disappoint me. The camera plays, to be sure, with her conventional male-gaze attractiveness, sustaining it through gangrene and a salt-destroyed face: exploitation leavened with a challenge not to give in to it. No doubt THE SHALLOWS fits the bill as a cheap summer thrill, but surfaces by definition are infinitely thin, and even to the shallows high tides roll in. Lively’s is a talent breaking through gauze, this film of Collett-Serra a plunge refreshing to take.

Check listings for viewing options.