“Under Paris,” “Deep Water,” “Thrash,” “Chum” — shark movies come so thick and fast these days that there’s barely any time between them to consider it safe to go back into the water. That being said, if this recent series of films is to be believed, regular old beaches are fine these days. It seems that toothy predators are increasingly looking for less obvious places to graze on moist human flesh: the site of a plane crash in the mid-Pacific, the City of Light, and now, in “The Devil’s Mouth,” a dark, dank, narrow cave on the idyllic coast of Thailand. This claustrophobic danger zone brings a dash of novelty to director Jeff Wadlow’s aquatic thriller, but the formula is familiar: five attractive young men on vacation, a bull shark very much in business mode, and a pecking order that most viewers can guess in five minutes.

It’s strange that the shark movie has lately joined the romantic comedy in the ranks of genres most favored for streaming, since its pleasures, from “Jaws” on, have been traditionally cinematic and communal: From the safety of your couch, a big white jump scare just doesn’t land the same way. A Prime Video release, “The Devil’s Mouth” sometimes seems ill-suited for the small screen, given the frequently squint-inducing darkness of its surroundings; On the other hand, the very loose progression of Aja Gabel and Myung Joh Wesner’s Black List script feels tailored to the requirements of second-screen viewing, with tensions between characters slowly and repetitively brewing between sporadic frenzies.

However, if the dialogue and characterization never get the better of pedestrians, those tensions at least lend malicious interest to the essential survival drama, with a strain of toxic friction evident from the start between likable protagonist Sarah (Kathryn Newton) and her narcissistic best friend Max (Lana Condor), a self-proclaimed “CEO of fun,” on her lavish post-graduation vacation. Both stars are better than their small roles demand, and Condor clearly relishes the opportunity to improve his healthy “To All the Boys” star persona a bit; perhaps its young fans will balk at how blatantly the film’s sympathies are in Sarah’s favor.

Or maybe not: Sarah has a pretty hard time from the beginning. The uncoupled fifth wheel on what would otherwise be a loving couples trip, with Max and their mutual college friend Adrienne (Tommi Rose) accompanied by their respective and equally vapid boyfriends James (Nico Hiraga) and Greg (Gavin Casalegno). Sarah is literally an afterthought when, at the end of a day of yacht charter in a picturesque cove, the other four set sail while she is still in the water, leaving her at the mercy of a blow. of jellyfish Cue an initial sea creature attack that is less bloody than those that follow, but perhaps the most disturbing and alarmingly constructed set-up in the film.

A brief apology from Max (“I’m trying to be responsible here,” he says, unconvincingly) doesn’t smooth the waters between the two by the time of the group’s next adventure: a remote coastal cave-swimming expedition led by local guide Wat (“The White Lotus” star Tayme Thapthimthong). A warning tone is soon set as the Americans, led by Max, repeatedly overturn the native Wat experience. (The safest cave route he recommends is marked on the map in green; the one they choose is marked in red. How many more flags do you need?) You can’t blame him for leaving them to their fate when, in several caves, devastated remains float to the surface, followed shortly by the dreaded fin slicing through the water.

How did the beast get into these narrow spaces? “I don’t think this is something we should solve now,” says one of the guys, and that’s fair, even if it frees up the writers. A more immediate priority is finding a route out of this network of caves, with the shark, having limited space to roam, following them around every corner. Needless to say, not everyone will make it out alive. The panic-inducing narrowness of potential escape routes marks a departure from the genre’s usual spatial dynamics, with Wadlow (recycling some of the atmospheres from his 2020 film “Fantasy Island,” minus the fantasy) and cinematographer James Kniest exploiting them more effectively in a pair of extended, suitably suffocating underwater scenes.

Surprisingly, it is the sharks’ appearances that lack bite. Denied a point of view or brought into close-up, the CG killer never feels a particularly distinctive or palpable presence, while his attacks take on a fairly predictable pattern. The gore, meanwhile, is unexpectedly low-key, which is a strange place for the film to exercise subtlety: a sea turtle washed out to sea with a cartoon-style bite taken out is the most visceral sight here, and the saddest. Human bait, on the other hand? You’ll have enough, friend.