This found-footage eco-horror cheapie—in which a waterborne parasite mutates into an unstoppable human-flesh-eating scourge thanks to the march of progress and attendant environmental carelessness—is not the cash-in you might expect from a Halloween release from the producers of Paranormal Activity. Directed by Barry Levinson (Diner, The Natural, Wag the Dog), it's the result of a sincere effort by a 70-year-old veteran filmmaker to speak about the world we live in now, in what he perceives to be the language of his audience. Give him an A for good intentions. Then there's the movie. Starring unknown actors and shot on consumer-grade (or lower) video, The Bay apes a hypothetical work of citizen journalism documenting a fictional disaster that killed off most of the population of Claridge, Maryland. Donna (Kether Donohue), a shell-shocked survivor, guides us through what she describes as a collage of footage confiscated by authorities: material captured by security cams, the TV station's cameraman, the camcorders of a tenacious emergency-room doc and a couple of beautiful young couples, and ample Skype and FaceTime exchanges. The format of an amateur doc allows Levinson to upend the structure of the disaster movie: We're told fairly early on what the scourge is and the extent of the damage. From that point on, there's nothing to do except watch as the characters—none of whom register as protagonists in a traditional cinematic sense—drop off one by one. When one infected townsperson dies, another trains the camera on the corpse; when the last character alive leaves town, the movie is over. It's the video-or-it-didn't-happen ethos turned into a narrative strategy.