Open Water (15)

Based on a true story, Chris Kentis's Open Water starts from a premise that will set you drooling if you love screen minimalism. Two holidaymakers diving in the Bahamas are left behind by their boat and stranded at sea. If you like ocean-going thrills, the best thing about this set-up is that it can't be long before the sharks start nosing around. But from a cinematic point of view, what's really intriguing is to see what Kentis will do with two characters up to their necks in water for the best part of 80 minutes.

Based on a true story, Chris Kentis's Open Water starts from a premise that will set you drooling if you love screen minimalism. Two holidaymakers diving in the Bahamas are left behind by their boat and stranded at sea. If you like ocean-going thrills, the best thing about this set-up is that it can't be long before the sharks start nosing around. But from a cinematic point of view, what's really intriguing is to see what Kentis will do with two characters up to their necks in water for the best part of 80 minutes.

This fascinating formal challenge goes a step beyond Alfred Hitchcock's 1944 film Lifeboat, which at least gave his cast the comfort of a dinghy. Open Water is, you might say, a desert island story without the island, or if you prefer, Jaws without Spielberg. Shot on digital video, Open Water has so far taken over $23m at the US box office - not bad for a film which Kentis and his wife-cum-producer Laura Lau photographed themselves on holiday and at weekends.

Plot-wise, there's not much to it. We get quite a bit of set-up, or just whiling away of time, before Susan and Daniel (Blanchard Ryan, Daniel Travis) hit the water. They load their car, banter about overwork, then arrive in the Bahamas where they sunbathe, shop and go to bed. The only ominous note, as they discuss their next day's dive, is that the organisers of the trip "seem pretty laid back". That's not the half of it. On the boat, there's a mistake counting off the divers as they surface, and Susan and Daniel are left drifting in the current.

At first, they're annoyed but relaxed. Then they get tense, and we start to wonder what they're going to do. More to the point, we wonder what Kentis will do once he's over the initial novelty of holding medium shots of two heads bobbing on the surface.

The sky gets darker, the clouds hang heavier, and Susan is bitten by a jellyfish - for me, the film's most unnerving moment, since there's little on earth or in sea more flesh-crawling than these improperly pretty, vampire parachutes. As for the sharks, they are surprisingly low on dramatic presence, despite being manifestly real: for the record, the film-makers mostly used grey reef sharks, their movements manipulated with chunks of tuna. But the fact that they are real mitigates the dramatic impact: they just don't have the menace of horror-movie sharks, even though once in a while a fin obligingly slices the surface. Mostly they hover, swishing in and out of view; somehow, we never feel they're especially bothered about devouring the characters, let alone the actors. They look as though they have better things on their minds - chunks of tuna, presumably.

Kentis gives his protagonists some rudimentary character development to keep us interested - at first they try to encourage each other ("This really sucks, but we're gonna get through this"), then petulantly bicker ("I wanted to go skiing," Susan sulks). But the dialogue is relentlessly banal, as if its only purpose were to give the actors something to do other than float. It's hard to care about this pair, partly because they're smugly unsympathetic from the start, partly because actors Ryan and Travis are so anonymously buff and handsome - perfectly competent but in this dramatic context, little more than good-looking flotsam.

The other reason we don't care is because there's no meaning to the story, it just happens. The screw-up on the boat is arbitrary, but has no ironic resonance. You could just about read something into the fact that the couple are so easily overlooked, and see this as a parable about the atomised, callous nature of contemporary society - but that would be stretching it. Or you could take the sequence where they drink coconut milk to a bouncy calypso backing, and conclude that they are being punished for their post-colonialist disregard for indigenous culture - but that would really be stretching it. No, this film is simply about two people who get stranded in the sea.

It's as if Kentis were saying, we've got a true story, real sharks and plenty of salt water - and you expect subtext, style, art? Of all the low-budget digital features to reach the big screen, Open Water is not only one of the roughest visually, it also has the least aspiration to be a film. Certainly, Kentis throws in plenty of looming clouds and blood-red sunsets, and the odd wildlife insert of hummingbirds and iguanas. But these look like stock tourist shots that Kentis and Lau took while off-duty. Bizarrely, Kentis puts more cinematic business - superfluous though it is - into the opening sequence of Daniel loading suitcases into his car than into the rest of the film.

The acceptance of harsh digital camerawork into the commercial mainstream has resulted in a lot of films, fiction and documentary, that consider a strong story to be enough, as if any degree of style were surplus to requirement. One example is this week's release Super Size Me: an enthralling piece of journalism (reviewed right), but not altogether a film (you might say the same of Fahrenheit 9/11). I imagine Kentis chose to present his story in such an artless fashion to make it more vivid, but the approach is counter-productive. Compare Kevin Macdonald's mountaineering docu-drama Touching the Void, where you can feel the frostbite and the fear, even though you know you're watching a reconstruction: that's because the film is made with precise craft.

Without such craft, it makes no difference that you have a good story to tell. What you're left with, as in Open Water, is a story that's barely even told: film without cinema.

j.romney@independent.co.uk