Venturing into the xenophobic terrain that helped to make Eli Roth's "Hostel" a unique horror destination, John Stockwell's "Turistas" takes full advantage of its intoxicatingly exotic backdrop -- it's the first American production shot entirely in Brazil -- to spin the creepy saga of a group of gringos whose fun-in-the-sun vacation turns deadly.

But while Stockwell effectively builds an unsettling, stifling atmosphere, layering all that impending dread on a workable foundation of chaotic culture shock and language barriers, it all begins to fall apart around the midway point, before completely unraveling into a confused, murky mess.

There's still enough good stuff to cut into a decent trailer, and that could be enough -- combined with those "Turistas Go Home" posters that have been popping up all over the place -- to initially draw young males lured by the promise of nude sunbathers and graphic gore, but word-of-mouth likely will ensure that this Fox Atomic release has a brief theatrical layover before taking the red eye to Blockbuster.

Among those heading up a treacherous mountain road in a speeding, rickety bus are reluctant traveler Alex (Josh Duhamel), his more gung-ho sister Bea (Olivia Wilde), her best friend Amy (Beau Garrett), lecherous Brits Finn (Desmond Askew) and Liam (Max Brown) and the bilingual Pru (Melissa George).

Not surprisingly, their reckless driver succeeds in totaling the vehicle, stranding the passengers somewhere between Rio and Sao Paulo. It turns out they're within walking distance of a cabana bar, where a group of them decide to dance and drink the night away.

Bad idea. They regain consciousness the next morning to discover they had been drugged and robbed of all their possessions.

Worse idea: They allow themselves to be led by a charismatic local (Agles Steib) deep into the Brazilian jungle and right into the lair of a gringo-hating, psychotic but righteous surgeon (Miguel Lunardi) in the business of black market organ transplants.

Up until this pivotal point, Stockwell and first-time scripter Michael Arlen Ross evocatively set the stage for all the impending nastiness, only to squander all that mounting tension in the translation.

Ironically, it's the very element that has been Stockwell's stock in trade (as in "Blue Crush" and "Into the Blue") that proves to be the film's major undoing: a protracted, dimly lit underwater escape sequence that is as dull as it is confusing.

It comes after another series of dark, hard-to-follow scenes leading to the speculation that they blew the lighting budget early on in the shoot.

The muddy results come in sharp contrast to the earlier, vibrant daylight sequences shot by Enrique Chediak and underwater cinematographer Peter Zuccarini that manage to find a suitably sinister undercurrent in all that warmly beckoning sunshine.