Labor Day weekend movie releases generally let you know that you've reached the utter dregs of the summer movie season; it's the cinematic equivalent of reaching into the cooler, only to find a Clamato and a diet peach soda floating around in the dirty, melted ice.

Nobody was expecting Shark Night 3D to be another Jaws, but with Snakes on a Plane director David R. Ellis at the helm, I'd at least hoped for some shameless, trashy entertainment. But this limp teens-in-peril fright flick doesn't even deserve to swim in the same bloody waters as Piranha 3D; frankly, there were more genuine jolts in Judy Moody and the NOT Bummer Summer.

And it's not just the gore-and-nudity-unfriendly PG-13 rating to blame, either -- apart from the occasional shark leaping toward the 3D camera, there's nothing scary going on here, so what we're left with is a bunch of blandly photogenic and indistinguishable characters taking turns getting eaten up in Louisiana swamp country.

The friends who become chum all go to Tulane University, where the Introverted Rich Girl (Sara Paxton) invites a bunch of people to her conveniently isolated beach house on a secluded island in the middle of the bayou. Her motley crew of cohorts includes the Nice Guy (Dustin Milligan), the Jock (Sinqua Walls) and his Girlfriend (Alyssa Diaz), the Vain Stud (Chris Zylka), the Bad Girl (Katharine McPhee), and the Nerd (Joel David Moore).

Yes, these characters actually have names in the movie. But they're such sketchy outlines of human beings that they don't deserve to have them listed here.

Throw in the random-girl-gets-chomped opening from Jaws, the shark-chases-a-water-skier bit from Jaws 2, some mean-looking local bumpkins (Joshua Leonard -- who's quite good in the current Higher Ground, incidentally -- and Chris Carmack), and a feckless local sheriff (Donal Logue), and you've got a thoroughly bland jambalaya of familiar ideas and waterlogged horror conventions.

Shark Night 3D has a grain of a fun idea when it comes to explaining how the sharks got there and what the ulterior motive behind the slaughter is -- hint: it's got something to do with everybody's favorite week of themed cable TV content -- but by the time the plot gets explained, we've already yawned our way through so much by-the-numbers carnage that it's hard to care.

Director Ellis really should know better: in addition to the wonderfully ridiculous Snakes on a Plane, he's the guy behind Final Destination 2, arguably the best of that gimmicky and over-the-top series of mayhem-based thrillers. How can such a master of grade-A junk make sharks in 3-D so utterly unengaging?

Shark Night 3D is the kind of experience that makes returning to school or work seem less grim by comparison.