One of those charming little documentaries that make you question whether the human race is really worth preserving, Irena Salina's Flow makes a fairly urgent three-point case: The first point is that much of the world has almost no access to clean water, yet impractical privatization schemes in Bolivia and South Africa, among other places, have deprived poor people of this vital necessity. Second, even when there's water available, the bottled-water racket leads companies like Nestlé to package it up and sell it back, causing lasting environmental damage to the places those companies are siphoning from. The last is the most frightening: We're using up the planet's water too fast, and very soon oil wars will be replaced by H20 battles. Salina's argument trends alarmist—is it really necessary to call water "blue gold," per activist/author Maude Barlow's formulation?—but generally rings true. Vomit-inducing shots of blood-red rivers running downstream from slaughterhouses prepare you for the shock of raw-sewage rivers. Aesthetics take a backseat to interviews, footage of water riots (no, really), and protests. Salina concludes with a cry for activism and intervention, but the case she's already built makes the battle seem unwinnable.