TENSE `OPEN WATER' NO FLOATING HOLIDAY.

Byline: Bob Strauss Film Critic

THE MICRO-BUDGETED shark thriller ``Open Water'' benefits from the simplest virtues. Concise storytelling. Deft characterization. Real sharks.

Pretty much the antithesis of ``Jaws'' - it doesn't so much manipulate fear as plunge us into a relentlessly unnerving predicament - ``Water'' may prove less jolting than expected for some. Yet the overall sense of dread is more vivid here, simply because it is multifaceted and for the most part unseen. I can't think of any movie that so well captures how the sea can be hostile to human existence the way it most commonly is.

Written by director Chris Kentis and shot by his producer wife Laura Lau, ``Open Water'' does something else that most movies with 100 times its budget can't manage. It presents a completely credible relationship. We recognize the bobbing couple, Susan and Daniel, from the moment we meet them through every emotionally wrought step of dealing with their harrowing predicament. And that's what makes ``Open Water'' truly nail-biting; you feel like it's happening to you and the person you love most.

An overworked L.A. pair played with comfortable intimacy by Blanchard Ryan and Daniel Travis, Susan and Daniel take a much-needed vacation to some unnamed Caribbean destination (the film was shot around the Bahamas). They halfheartedly do some touristy stuff, nearly but don't have hot tropical sex and chase bugs around their hotel room.

Recently certified, their one big activity is a SCUBA trip out to an ocean reef. Due to a head miscount, the boat departs before Susan and Daniel surface. Caught in a strong current and logically expecting imminent rescue, the pair makes assorted, useless attempts to help themselves but, mainly, tread water.

And as the hours drift by, they go through the stages of hope, denial, panic, recrimination and intensified love for one another. At regular intervals, sharks come in close or pass beneath their finned feet. But hunger, cold and the general physical and psychological wear of floating around in the middle of nowhere could be just as dangerous as any sea scavengers. And the biggest fear of all? Drifting apart, which seemed such a minor proposition on land, is now a life-and-death issue.

Well-fed local reef sharks swam around the unprotected actors and Lau, and while the effect isn't Spielberg-precise, the scariness is palpable in a way mechanical Bruce could never have been. The video quality isn't the highest, which makes for an annoying, soft-edged fuzziness on land but lends itself to beautiful, properly disorienting light and density effects in the water.

But it is the actors' and director's ability to put us inside Susan and Daniel's wet suits - and equally as important, their heads - that gives ``Open Water'' its real bite.

Bob Strauss, [phone]

bob.strauss(at)dailynews.com

OPEN WATER - Three and one half stars

(R: nudity, language, shark violence)

Starring: Blanchard Ryan, Daniel Travis.

Director: Chris Kentis.

Running time: 1 hr. 19 min.

Playing: Playhouse 7, Pasadena; ArcLight, Hollywood; Century 14, Century City; The Grove, Farmers Market; Criterion 6, Santa Monica; Edwards 21 MegaPlex, Irvine; AMC 30 at the Block, Orange.

In a nutshell: Low-budget thriller about a couple abandoned by their diving boat in shark-infested waters boasts pitch-perfect character work and persuasive, realistic suspense.