‘The United States does not keep active records of how many people get sick from our water supply every year,” the former senior attorney for the Natural Resources Defense Council, Erik Olson, says in Irena Salina’s documentary “Flow.” “A lot of people think they don’t have to worry about their water supply because they go out and buy bottled water. Well, we have news for them. In fact, a lot of your exposure to many of the chemicals comes from the simple act of showering in them.”

That’s just one of the many inconvenient truths that Ms. Salina’s film, which opens Friday at the Angelika Film Center, is trying to expose. Even if it merely presents these shocking developments as hearsay rather than providing any concrete evidence, the film will likely instill a deep sense of worry in any viewer hearing them for 84 minutes.

Spanning four continents, “Flow” offers an expansive look at the global water crisis, but only in a geographical sense. Footage is gathered from France, India, Bolivia, South Africa, Lesotho, and America, just to name a few places. But for the most part, the film comes off as little more than agitprop. It taps into a conflict on the most surface level without actually tracking the causes and effects over time, as a serious documentary should.

Take, for example, the film’s case study of the water crisis in Bolivia. When the country privatized its water supply, it rendered a basic necessity unaffordable for the poor. That’s quite an extraordinary story in itself, and would surely make for a compelling film. Instead, “Flow” shows bare snippets of polluted water streaming from a slaughterhouse, angry locals protesting, and seemingly slimy executives from global corporations who serve as contractors in Third World countries with no water-supply infrastructure of their own. Ms. Salina did not confront the executives after she got them to state their names for the camera. A separate vignette follows a lawsuit against Nestlé’s water-bottling plants in Michigan for damaging the surrounding ecosystem, but Ms. Salina apparently made no effort to reach a company spokesman. Where’s Michael Moore when you need him?

“Flow” certainly alerts viewers to the global water crisis. Halfway through, all the talking heads are describing it in unison as an apocalyptic scenario. Yet because of its broad scope, the film often feels unorganized and free-associative. It attempts to incite activism, but moviegoers can easily walk away without knowing precisely what “Flow” wants us to do — aside from boycotting bottled water, that is. Indeed, it comes across as too little and too late in terms of making any kind of a splash in this election year.