Sequels that are really more like unrelated entries in an anthology series are nothing new at all, especially in the horror & thriller genres, so the fact that 47 Meters Down: Uncaged has absolutely not one blessed thing to do with 47 Meters Down, the banal shark film from 2017, is not surprising. That it also has absolutely not one blessed thing to do with being 47 meters below the surface of the ocean is not surprising either, though it is annoying.

Anyway, like any good slasher movie - and structurally, that's exactly what Uncaged is - it's more about the formulaic elements than the plot specifics. So what do we have as far as formula? Well, we've got a pair of sisters who don't get along particularly well going on a swimming excursion in Mexico. One of them is the boring one, one is the lively one. The swimming excursion ends up going off-book, and they get stuck facing sharks. And in a very weird point of overlap indeed, both movies actually get worse when the sharks show up: both get a pretty substantial amount of mileage from the visceral impact of setting their action in a dark watery space (47 meters below the surface then, a series of claustrophobic tunnels in a sunken Mayan temple now), and the irresistible power of suggestion. Underwater is a bad place for we humans to be, and so is the dark, and when you put them together and have just enough light to reveal what a tight, inescapable rock prison the water has filled, you have the stuff of real good cinema that goes right to your guts. Throwing CGI sharks at that somehow just makes it all tawdry.

And the CGI sharks in Uncaged are, like, real fucking bad. In addition to being a by-the-books slasher movie, it's also basically The Descent with sharks, so they're some real doozies of over-the-top design. Huge pasty-white blind cave sharks, with milky white eyes that are legitimately creepy the first time we see them, and then just make the sharks look like overdone CGI zombies thereafter. The flabby white skin never looks creepy. And like the best slasher movie skillers, the sharks prefer to do their work in the form of jump scares, carefully arranging themselves to hide around corners so that they can persistently dart forward when it will most effectively rattle the human characters. At one point, a shark zips right out of a tunnel only inches larger than itself, like a monstrous toothy tube worm. I question whether Ernest Riera and Johannes Roberts (the latter also directs) should be writing shark movies.

Our victims begin with stepsisters Mia (Sophie Nรฉlisse) and Sasha (Corrine Foxx, daughter of Jamie Foxx), who are in Mexico as part of the archaeological work being done by Mia's father Grant (John Corbett). He and Sasha's mother Jennifer (Nia Long) are concerned that the two girls aren't getting along, and in particular that Sasha's easy popularity at their international high school is built at the direct expense of Mia, who has become a punching bag for the local mean girls. So they've arranged a trip on a glass-bottom boat that neither girl particularly wants to go on, but both put on a brave face about it. Sasha's friends have a better plan: Alexa (Brianne Tju) has learned of the location of a beautiful pool in the jungle right above the entrance to Grant's submerged temple, from having slept with Grant's assistant Ben (Davi Santos), and she recommends that Sasha and their other friend Nicole (Sistine Stallone, daughter of Sylvester Stallone) go for a swimming and diving adventure. Oh, and Mia might as well come to. Before you can say "obviously ill-advised teenage bullshit", they've gone for a swim into the first big chamber of the underwater ruins, where they encounter two things. One is Ben. The other is the enormous cave shark that eats Ben. Oh, and a third thing is some kind of cave tetra that is mostly unexceptional beyond the fact that provides the writers with a chance to explain how cave fish can grow translucent and blind, though not how they can also be 15-foot-long apex predators in an environment that has been sealed from outside contact for at least several hundred years. The other exceptional thing about the cave tetra is that it screams - it actually, literally fucking screams like a howler monkey, despite being A) a fish B) that lives underwater. The implication is that this is what calls up the sharks.

Anyway, the shark causes a cave-in, and the girls must carefully pick their way through the ruins to find the other entrance that Grant, Ben, and second assistant Carl (Khylin Rhambo, one of the very best names I have ever encountered in the cast list of any work of media) have been excavating all day. By the time they find this exit, it is not surprising that the six people who remain alive in the ruins after Ben's demise have been reduced in number. It is also not surprising who gets eaten, nor in what order; the film is careful to make certain characters anonymous and certain characters inordinately unlikable, so that we always keep our eyes on the obviously pre-ordained endgame.

There is, to be sure, something amusing in watching the ancient narrative beats of the slasher movie replicated down to the tiniest detail with sharks. It possesses a strange mixture of the desperate and the pathetic. Shark movies have always been predicated on the idea that their chosen monsters are massive, sleek eating machines; that they would have the cunning malice to be slasher killers is almost antithetical to the point. But, hey, cave sharks. All bets are off.

Mostly, though, it's just boring as hell. The sharks, being shark-shaped, have pretty much just two attacks: swoop in fast from the left, and swoop in fast from the background. If it's the former, you're dead. But if it's the latter, you always have a chance of quickly swimming into one of the many rocky niches scattered in the temple, which is why there are something like five different shots of a shark poking its nose into a space too small for its body while a teen girl thrashes and screams in the foreground. Once and only once - it's Carl's death scene (which is also the scene in which he's introduced, though he lasts longer than poor bastard Ben) - the filmmakers get some mileage out of fragmentary shots of the sharks floating across space, more perceptible as enormous curves of white than as giant fish. Otherwise, it's one-death-fits-all, and it gets enormously dull by the time the film finally arrives at its legitimately creative final sequence (which is not, I am heartbroken to report, an asinine twist of such towering bullshit as the last film boasted; it is merely a neat little "one damn thing after another" callback). In the meantime, the film belabors our time with four terrible main characters: Mia is the only one written with any level of complexity, and Tju is the only one of the actors doing more than the bare minimum to put her lines across (Stallone isn't even doing that much).

There's something here: the underwater ruins are a suitably otherworldly, spooky location, and flashlight beams in murky water are a great way to build some instant atmosphere. Take out the sharks, and just make it a fight for survival in an unnavigable cave system with the oxygen tanks providing a steady ticking clock, and maybe 47 Meters Down: Uncaged would have something. It would, to be sure, be neither 47 meters down, nor would there be a cage to not be in, but that would be a welcome price to pay for a film that accentuated its legitimate strengths, rather than buried them under two tons of clammy CGI shark meat.