C-

“Piranha 3D” opens with its best bit—a guy is attacked by a horde of the flesh-eating creatures as he fishes from his little boat on Arizona’s Lake Victoria. What makes the sequence amusing is that the unfortunate fellow is named Matt (though it’s Boyd, not Hooper) and played by Richard Dreyfuss, whose presence can’t help but call “Jaws” to mind. It’s a homage, of course, but one that seems right, given that Dreyfuss was absent from “Jaws 3D” and finally makes his appearance in the format in a similar shaggy-fish story.

But otherwise it’s not too bright of the filmmakers—headed by director Alexandre Aja, an old hand at this sort of stuff (“High Tension,” “The Hills Have Eyes,” “Mirrors”)—to remind the audience of “Jaws,” which was a much better movie than this one, yet another attempt to enliven the creaky horror genre by doing a remake in the currently popular 3D (see also “My Bloody Valentine” and “Final Destination 4”). Nor is it all that good an idea to remind them of 1978’s “Piranha,” a Roger Corman cheapie that was hardly a classic but did boast a cheekily winking script by John Sayles and witty direction by the young Joe Dante. Apart from the opening with Dreyfuss, the about the only hint of genuine humor here comes from a sign at a big lake bash that reads “Dying to Get Wet”—not exactly Oscar Wilde. Unless, that is, you care to count inserts like one in which a piranha is seen gobbling down a guy’s severed penis (ho, ho).

Anyway, these aren’t just your ordinary run-of-the-mill piranha. No, they aren’t the super-piranha fashioned for military use that Sayles’s script contrived. These are prehistoric piranha, released into the lake by an earthquake that created a rift that allowed them to swim from a lake under the existing one, where they’d survived for millennia. That, at least, is the explanation of Mr. Goodman, the wacky old coot who runs the local fish store—Christopher Lloyd in full goofy throttle in a bit that might be called “Back from the Past.”

And wouldn’t you know this all happens on Spring Break, when hordes of oversexed, heavily-imbibing college students have descended on Lake Victoria for their big party? The kids spend most of their time gyrating at the town docks, egged on by sleazy video promoter Derek Jones (Jerry O’Connell), who’s shooting a “Wild Wild Girls” piece that includes lots of naked boobs that are among the things repeatedly thrust out into the audience for 3D effect. Derek’s unsavory business is connected with the local population via his hiring of teen townie Jake Forester (Steven R. McQueen, the brooding brother of “The Vampire Diaries”) as his location scout. Jake’s the son of Julie Forester (Elisabeth Shue), the local sheriff who must deal with the fish crisis. And since he’s supposed to be babysitting his siblings, little Zane (Sage Ryan) and Laura (Brooklynn Proulx), his sneaking away to sail off into danger with Derek puts them in danger, too, since they immediately disobey his instructions to stay home.

Of course, the human flotsam and jetsam—which also includes Jake’s would-be girlfriend Kelly (Jessica Szohr), Derek’s chief model (Kelly Brook), Deputy Fallon (Ving Rhames) and the state expert (Adam Scott) called in to help—are entirely secondary to the fish, which are supposed to be really scary. They’re not, of course, mostly because the CGI used to fashion and then superimpose them on the widescreen footage shot by cinematographer John R. Leonetti isn’t all that great; the piranha look like plastic critters from an old “Outer Limits” episode, and when they’re shown en masse, the result is usually so murky that the impact is minimal. The makers try to ratchet things up with lots of gruesome dismemberment bits—not just that penis but some floating eyeballs and torsos literally ripped in two, as well as whole bodies reduced to masses of bloody glop. But the more gore they throw at you, the less it matters. It also doesn’t help that the big capper they save for their closing shot is included in the ubiquitous trailers for the movie, so that it comes as no surprise whatsoever.

And the human portion of the equation serves as nothing more than a smorgasbord for the toothy fish. You know pretty much which of the dishes are going to survive the ordeal and which are expendable, or even deserving of getting turned into hamburger, so all the daring escape scenes lack suspense. (O’Connell, for example, is playing such a loathsome jerk that it’s inevitable he’s fated to suffer a gruesome demise. He’s so overboard—if you’ll pardon the pun—that a performance like this could end his career. But then he survived “Tomcats,” so probably not. And need one point out the irony of lampooning exploitation in a movie that’s nothing but exploitation itself?) As for the characters we’re supposed to care about—the sheriff and her brood, in particular—they’re all such boneheads that you might wish the piranha were a little more successful than they turn out to be. The actors play them with a seriousness that’s admirable under the circumstances, though.

The last scene of the movie practically promises a sequel. Given the premise that ending suggests, it might be called “Piranha: The Revenge.” After all, look how well that worked out for the “Jaws” franchise. Still, “Piranha 3D” is certainly better than James Cameron’s “Piranha 2: The Spawning,” from 1981 (which he’s probably removed from his resume), and if you’re in the mood for such schlock, you could do worse. That’s what’s called faint praise.