Walking into "Shark Night," there was already a lot going against it, not the least being a PG-13 rating that seemed to go against everything this kind of fun B-level slasher thriller usually stands for. That it was being released theatrically in 3-D was all the more suspect. Imagine 2010's initial 3-D release of "Piranha" without the rampant nudity and over-the-top violence and gore and what you'd have left is, well, some pretty scenery and a lot of bad dialogue. If director David R. Ellis (2006's "Snakes on a Plane") makes certain of anything here, it is the danger of preconceived notions. Far-fetched though it is, "Shark Night" works better than one could possibly imagine. It retains enough deadly mayhem and suggestive nudity (not to mention tight backside close-ups) to not feel the least bit watered-down, then does one better by treating its story and characters with an agreeable balance of the serious and tongue-and-cheek. As unnecessary as the format is in general, even the use of three dimensions is comparatively effective and unobtrusive.

With finals over and a long weekend before them, a gaggle of fit, chiseled Tulane University students are ready to let loose and unwind. Their destination: Sara's (Sara Paxton) family's secluded island chalet on Louisiana's Lake Crosby. Haunted by an accident she was involved in as a teen, she hasn't been back to her old stomping ground since she left for college three years ago. Before Sara has time to work out her conflicted emotions, she and her classmates—among them, pre-med nice guy Nick (Dustin Milligan) and his roommate, the seventh-year Gordon (Joel David Moore); tattooed wild girl Beth (Katharine McPhee); art class model Blake (Chris Zylka); and NFL-bound athlete Malik (Sinqua Walls) and girlfriend Maya (Alyssa Diaz)—are besieged by blood-thirsty sharks that have somehow escaped the gulf and made their way into friendly waters. As night sets in and the group struggle to find help for one of their injured friends—cell phone reception doesn't work, natch—a danger running far deeper than the surrounding sea creatures slowly reveals itself.

Their plot's jumping-off point and basic trajectory are decidedly standard, but first-time screenwriters Will Hayes and Jesse Studenberg do a plausible job of coming up with reasons for the characters to consistently find themselves vulnerable around water. Lo and behold, it's not as simple as just staying on shore, the threat level, as a result, remaining at a high pitch throughout. With little down-time outside of a drawn-out, obligatory scene where Sara explains to Nick why she hasn't been back since she went away to college, the film wastes no time pitting the dwindling ensemble against vicious sharks (pulled off via a professional, mostly seamless mix of animatronics and CGI) who don't exactly sit idly by. A couple good jump scares result, including one that rivals the infamous Samuel L. Jackson death scene in 1999's "Deep Blue Sea," all the while the story tosses in a timely, sociological comment on modern society with references to everything from "Shark Week" to "Faces of Death" to "March of the Penguins."

The cast is above-average, if not consistently in the acting department than certainly in regards to their shirtless and/or bikini-clad physiques. As Sara, Sara Paxton (2009's "The Last House on the Left") is a sympathetic heroine, if a tad mopish, and Dustin Milligan (2009's "Extract") is a likable male lead as Nick. The choice to have the hunkiest of the lot, Chris Zylka's (2011's "Kaboom") Blake, arguably be the most sensitive was a neat non-stereotypical change of pace. Joel David Moore (2009's "Avatar") and Katharine McPhee (2008's "The House Bunny") share an easy chemistry as the flirtatious Gordon and Beth, bonding early on over a game of inflatable raft-set beer pong. More questionable is the uncomfortable position director David R. Ellis puts Sinqua Walls, as Malik, in; perhaps having the sole black character end up stalking the waters with a spear in hand should have been rethought. Finally, Chris Carmack (2010's "Alpha and Omega") and Joshua Leonard (2009's "Humpday") are as smooth at being smarmy and spiteful as they're supposed to be in the roles of rough-and-tumble townspeople Dennis and Red.

The last seconds of the finale of "Shark Night" are a letdown, ending in a derivative, throwaway stinger that does its surviving characters no favors and fails to satisfyingly wrap up all the loose ends. Before this, however, the film is rather enjoyable, even gripping, in its own conventional but frequently inspired way. Ellis and cinematographer Gary Capo (2004's "Cellular") bring a stylish streak to the storytelling, and the use of sped-up editing is especially crafty in portraying the long journey to their vacation destination in roughly a minute's time. Topping the experience off is a post-credits coda directed by Dustin Milligan as bizarre, original and out-there as any tag in memory. It may come as a spoofy, mocking aside to the overriding drama of the feature proper, but it's clever all the same and proves the actors and filmmakers involved are well aware that they haven't just made an awards contender. Get in the correct mindframe and "Shark Night" delivers a tasty blend of the predictable and unexpected.