Grade: C

This little Sundance Festival favorite aims to be the new “Blair Witch Project.” It’s gotten a reputation as a poverty-row version of “Jaws”–a picture that will make people equally terrified about the perils of the ocean, but that was made on a tiny fraction of Spielberg’s budget. And “Open Water,” written, directed, edited and co-produced by Chris Kentis, does manage to ratchet up the tension as a couple go on a group scuba dive during a vacation in Bermuda, get accidentally left behind in the deep by their charter boat, and struggle to survive as they’re carried ever further out to sea and menaced by sharks, among other dangers–and it does so through very modest means. But it’s rarely as gripping as it wants to be; for the most part it treads water just as its lead characters do.

Certainly the moments when we actually see Daniel (Daniel Travis) and Susan (Blanchard Ryan) in the water as sharks swim about them are frightening–especially since it’s abundantly clear they’re not created by expensive special effects but were shot in real circumstances.

But those episodes are relatively few and brief. And the rest of “Open Water,” to be perfectly frank, is pretty tedious going. It begins with a long sequence, covering more than a quarter of the running-time, showing the duo packing for their trip, checking into their hotel, doing some sightseeing, enjoying the beach, and trying to get some sleep though bothered by an insistent fly. Then there’s a protracted scene of preparation for the dive, dominated by their guide and a rather rude passenger who’s forgotten his goggles and so isn’t allowed to participate (he’s part of the explanation of how the divers are miscounted as they come back aboard and our protagonists are left behind), followed by some travelogue-like underwater shots as the passengers frolic about.

All of this preparatory matter would have made sense had it added some dramatic heft to the lead characters, but it really doesn’t–they’re as bland and generic by the time they’re lost in the drink as they were when they were loading their SUV. (In that respect this “Water” isn’t at all deep.) As they alternately bicker about whose fault their predicament is and what to do about it, and try to bolster one another’s spirits, you’re as likely to find them annoying as sympathetic. There’s an improvisational feel about much of what they say, which sounds like a virtue, except for the fact that as improvisation it’s rather flat and perfunctory. And though one can admire the readiness of Ryan and Travis to become human raisins in the service of art by staying so long in the water, the sad fact is that neither evinces any great thespian ability.

Still, it must be said that as the film reaches the final quarter and the air of desperation escalates, “Open Water” becomes increasingly effective, because it’s the situation, rather than the characters, that matters. And the fact that it undercuts expectations by going for an ending that, in this day of incessant crowd-pleasing among Hollywood movies, many will find shocking is a point in its favor. Technically the film is obviously a barebones effort, with the camerawork by Kentis and co-producer Laura Lau coming across as strictly functional, without any real hint of style.

But whatever the picture’s failings, you have to respect filmmakers and actors who are willing to take such risks to fashion their little exercise in suspense, and if the result doesn’t achieve the nerve-wracking heights they’re aiming for, it does manage to be unsettling for much of its second half and more than that toward the close. At only 79 minutes, it also recognizes the thinness of plot and the damage that would be done by extending it to undue length. Perhaps the picture will have greater impact in theatres near to the seashore, or among viewers who scuba dive themselves. But “The Blair Witch Project” didn’t really live up to its exaggerated advance buzz, either, and it still gave a great many viewers the willies. Maybe “Open Water” will, too.