For Watermark, the two co-direct, traveling the world to document the complex interaction of man and water. Aided by cinematographer Nick de Pencier, the filmmakers aim their cameras at the landscapes surrounding the world's great waterways, as well as at the humans who live in and around them. We bear witness to the construction of the Xiluodu Dam in China and later join in a gathering of Hindus seeking to bathe away their sins in the Ganges. The footage is often alarming, as when the chemical waste from a Colombian leather factory is tracked to a nearby river from which families draw water. Visually, Watermark is exquisite, but as a narration-free documentary, it's a thematic muddle. Trying to grasp a narrative thread amid the constant continent-hopping proves wearying, and if this is a film about water, why stop to watch Burtynsky pore over the proofs for his latest book? Are we meant to fear for the natural world, or stand in awe of the man taking the pictures?