JUST when you thought it was safe to go back into the cinema, Open Water rises from the depths of obscurity to try to scare the flippers off the movie-going public.

Costing around US$130,000 to make, it is by far the cheapest movie to hit cinema screens this year, and it attempts to prove, much in the same way as The Blair Witch Project did, that you don't need big bucks to make a frightening and disturbing film.

Based on a true story, Open Water focuses on a young married couple, Susan (Blanchard Ryan) and Daniel (Daniel Travis), whose Caribbean holiday turns into a nightmare when they find themselves stranded in the middle of the ocean during a diving trip.

Faced with man-eating sharks, impending storms and bobbing around miles from land, the couple must rely on each other, despite their already-strained relationship.

The key word for this film is "cheap". Straight away it is obvious that this film does not have any significant financial backing - in short, it looks likea B-movie.

Whereas Blair Witch - with which Open Water has been repeatedly compared - overcame this problem by incorporating a documentary-style stance as its ethos, this shark tale does no such thing.

As a result, instead of coming across as stark and realistic, it merely comes across as shoddy and second-rate.

And the whole affair isn't helped by the sheer lack of inventiveness by the director, Chris Kentis.

Don't expect any fancy zoom or pan shots here, as Kentis sticks to the basics - shots of the couple in the water, spliced together with shots of people partying on the safety of the beaches.

It's as obvious and blatant a film as you are ever likely to come across.

But it's not all bad. The acting is surprisingly competent for a cast of relative unknowns, and the action is never left wanting, providing a continual stream of tension for the audience.

This reaches its peak during the night scene when the screen remains black for many seconds until flashes of lightning uncover what's really going on amid Susan's screams.

Unfortunately, this only lasts for a couple of minutes and could have been put to better use.

Open Water relies on the unknown to hook and reel in the audience.

When Susan remarks "I can't stand not knowing what's beneath me", we are right there with her.

But as this is its strongest weapon, it's also the film's biggest downfall. The tension is there, but so often feels like an anti-climax.

Overall, it's a "big fish" story. It could have been so much better, but will always be the one that just got away.