Turistas is as curious a mix of strengths and weaknesses as you're likely to find in a modern horror movie. Its best parts are truly superlative, but often within the same set piece (or even the same shot), John Stockwell's movie is undone by pointless red herrings and lame-brained plotting. For starters, Turistas would have been better off concentrating on the extreme disorientation of being lost and penniless in a foreign country. Stockwell makes coastal Brazil the same kind of exotic youth paradise he made Hawaii in Blue Crush, so the sudden overturning of that world seems all the more abrupt. But, in a possible attempt to duplicate the success of Hostel, the film introduces black-market organ harvesters as villains, which echoes the torture milieu from Eli Roth's movie (to say nothing of how it stigmatizes Brazilians). Since this doesn't seem like the correct thrust for the story, these sections, while delightfully squirmy, lack a certain necessary significance. But even when Turistas is mostly going in the right direction, it still makes bizarre narrative errors. For example, at one point, the travelers' de facto tour guide takes a dive in shallow water, cracking his head open. That should be a major crisis point for their fortunes, but it ends up totally moot when the man makes a full recovery within ten minutes of screen time. Why even include it? Even the dynamite centerpiece -- a hold-your-breath chase sequence through dark underwater caves, where the characters must desperately search for elusive pockets of air -- is less effective than it should be, because Michael Arlen Ross' script misses the boat on several smart payoffs. Turistas has much to recommend it in the genre of films where ordinary events spiral out of control, but it leaves a lot to be desired as a horror.