Director Alexandre Aja's career has been varied since rightfully gaining notoriety with 2005's terrifying "High Tension," doing right with 2006's "The Hills Have Eyes" remake before failing to make much out of an inspired premise with 2008's "Mirrors." This time around, Aja knows exactly what he's doing. A loose update of 1978's respectable Roger Corman-produced, Joe Dante-directed original—in and of itself a knowing rip-off of "Jaws"—"Piranha" takes the general idea of the deadly title fish attacking and then joyously cranks the carnage level up to a thousand. Peter Goldfinger and Josh Stolberg (2009's "Sorority Row") are credited with penning the screenplay, but who's kidding who? If the script was jotted down on anything other than a paper napkin, it would come as a surprise.

Just as spring break is getting underway in the picturesque Arizona hot spot of Lake Victoria a quake rattles the underwater floor, creating a subterranean rift that unleashes schools of ancient, voracious, man-eating piranha. After a local fisherman (Richard Dreyfuss) shows up dead, local sheriff Julie Forester (Elisabeth Shue) suspects trouble is afoot. As she and geologist Novak (Adam Scott) continue their investigation—Julie wants to shut down the lake, but is urged not to lest the town financially lose out big time during its most prosperous week of the year—the piranha move ever closer to a buffet of unsuspecting, hard-partying revelers.

"Piranha" is thematically vacant. The characters are stock figures all the way. The dialogue is bad, but also campy enough to let the viewer know the makers are in on the joke. It's no coincidence that Richard Dreyfuss (2009's "My Life in Ruins") cameos, more or less reprising his 35-year-old role from "Jaws," and that Christopher Lloyd (1999's "Baby Geniuses") shows up as a scientist with warnings of doom. When Lloyd excitedly yet gravely exclaims, "This particular kind of piranha vanished off the earth two million years ago!" it is impossible not to get visions of Doc Brown dancing in your head. Adding to the allusion is a bad-ass Elisabeth Shue (2008's "Hamlet 2") as sheriff and single mother Julie Forester, a fellow alum of the "Back to the Future" trilogy. Had Lloyd ended his scene with a "great scott!" utterance, it might have simply been too much to handle at one time.

Because there's little to think about and the gaggle of protags and victims are roughly as deep as a pamphlet detailing famous Jewish sports legends, the first half is a tad slow going. Once the piranha reach their destination and attack, however, things hit into overdrive. The remaining forty minutes are a nonstop, action-packed parade of nudity and gore, spilled guts and severed body parts, director Alexandre Aja unable to hold back his boundless glee in devising different, unthinkably gruesome ways for people to die. One girl gets her hair caught in the motor of a speed boat and suffers the outrageously awful consequences. Another gets violently pulled through an inner tube after her ass is chewed off. The wet T-shirt contest host (Eli Roth) gets so excited he positively loses his head. Further down the lake, Julie's teenage son Jake (Steven R. McQueen) has been hired as a location scout for sleazy porn producer Derrick Jones (Jerry O'Connell) and is currently stranded on a fast-sinking boat with school crush Kelly (Jessica Szohr) and younger siblings Laura (Brooklynn Proulx) and Zane (Sage Ryan). Once she hears about this, Julie throws down her taser gun—yes, she uses it on fish—and leaps into rescue mode. Meanwhile, the smarmy sex entrepreneur unknowingly races toward the worst fate a man of his profession could possibly dream of. We'll leave it at that.

Tongue-in-cheek and all in the name of fun, "Piranha" knows how completely inconsequential it is, yet never stops dreaming up imaginative ways for death and destruction to occur. Humorous, thrilling, and finally suspenseful during a taut climax that finds terrified passengers trying to escape a submerging boat with unstoppable killer fish chomping at their heels, Aja pushes the R-rating to the limits with so much blood spilled the screen occasionally is washed over in crimson. That's how it should be, and that's how it is. "Piranha" is dumb as a box of hair and could have been more involving at the onset were there something besides violence to cling to, but it nonetheless delivers in spades precisely what it sets out to.

Special note: Shot in two dimensions and converted to three for theatrical release, "Piranha" doesn't look half bad, mostly thanks to a number of perfectly gimmicky shots and the majority of the film taking place in the bright sunshine. It's definitely a step up from the totally ineffective, off-puttingly murky 3-D presentations of "Clash of the Titans" and "The Last Airbender," but outside of adding to its drive-in movie allure it's still little more than a greed-induced flourish. Thank goodness it never pretends to be high art.