Workaholic couple Susan (Ryan) and Daniel (Travis) jet off to a tropical holiday spot for a well-earned week off. Keen on cramming in some scuba action they take a crowded boat out to a popular reef, 15 miles from shore. But a headcount error leaves them stranded.
With its small-change budget, FX-free execution, two-person crew and primal-fear-tapping concept, this has already invited comparisons with The Blair Witch Project. If you're desperate for a convenient, soundbitey boil-down, 'Blair Witch meets Jaws' kind of does the job, but, despite Open Water's merits, don't be hoodwinked into thinking it's the equal of either of those movies.
Unlike Blair Witch, Kentis' true-life thriller keeps the camera out of the characters' hands and firmly in 'impossible observer' mode, making its shaky, grainy look somewhat less appropriate - especially as Kentis and producer Laura Lau (both credited as cinematographers) are partial to inserting the kind of 'arty' close-up shots of dancing sunlight on rippling water you'd expect from Terrence Malick.
Plus, its admirable insistence on ultra-realism may prove off-putting for some: there's no getting away from the fact that Daniel and Susan are very average middle-class professional types. The unrushed set-up's tour of their little routines and numerous foibles, while brave and well-acted, does encourage fidgeting.
But it's not important to like the central couple, only to relate to their situation, and it's here that Open Water excels. Kentis pulls us in tight to his helpless, drifting protagonists, bobbing on the surface alongside them. Once the nightmare begins, we're only granted the occasional dip below; one particularly terrifying, second-long subaquatic glimpse reveals an ocean crammed with darting sharks, before returning us to a deceptively calm surface.
This aids the gradually ballooning sense of anxiety, the feeling of being insignificant when compared to nature's uncaring magnitude and the palpable fear of what's lurking in the murky depths beneath your dangling, very edible limbs. As it dawns on the couple that they've slipped several links down the food chain, you're right there with them. This isn't your average against-the-odds survival story.
Kentis and Lau keep things untinged by sentiment and are more concerned with churning your gut than making you punch the air.
Open Water is a great calling card ù and the worst press for sharks since Spielberg set Bruce loose on Amity ù but the slow set-up is likely to deny it untrammelled multiplex success.