Starting with the title, there’s an unusual depth to The Weight of Water. Screening at the Vancouver International Mountain Film Festival on February 28, Michael Brown’s documentary follows Erik Weihenmayer’s 21-day attempt to kayak the 300-plus kilometres of the Colorado River running through the Grand Canyon.

“I dunno if there’s a list of the most quin­tessential white-water runs in the world, but the Grand Canyon has to rank,” says the filmmaker, reached at his office in Boulder, Colorado. “The water in the canyon is awe-inspiring. It’s one time when awesome is appropriately used, because it is.”

No less awe-inspiring: Brown’s subject Weihenmayer has been completely blind since his teens, robbed of his sight by the rare disorder juvenile retinoschisis. The duo first documented Weihenmayer’s successful bid to summit Everest in 2001’s Farther Than the Eye Can See, and their subsequent two-decade friendship lends an intimacy to The Weight of Water that might have eluded another filmmaker. As the canyon’s rapids grow in size and ferocity, Weihenmayer’s fear increases, and Brown’s camera refuses to look away.

“Hollywood studio films spend a lot of time on the characters’ faces because then the audience gets to project an emotion,” says Brown. “And Erik is perfect for that because he often doesn’t realize that you’re filming him. In those moments he’s just there, he’s just being himself, very vulnerable, not aware of the camera.”

Aiding Weihenmayer in what frequently looks like an act of madness is river guide Harlan Taney, who communicates with his partner by radio. Expert, precise, unflappable—he’s the kind of guy anybody would want on an adventure like this. Except that Taney is wrestling with demons of his own, and his motivations are anything but simple.

“I like films that peel back the layers rather than blasting you with it from the beginning,” remarks Brown, whose final cut benefited from an unusually long editing process. He fathered two children while working on The Weight of Water. He also got deeper into Taney’s back story, hence a psychological arc that lifts the film out of the ordinary, in which courage and desire in the face of death are linked by trauma. This is one of the few outdoor-adventure documentaries likely to move its audience to tears at least twice.

To be sure: it’s also the kind of rugged, wilderness-infatuated effort that VIMFF attendees love. Brown made the unusual if not practical choice to also take the Grand Canyon by kayak, and the film’s immersiveness—its terrifying view of the churn that awaits, for instance, at Lava Falls—has the weight of direct experience.

“The journey of the filmmaker is also legitimate, as is the audience’s journey, as is the characters’ journey,” offers Brown. “To pretend you have some detachment or that you have to control every situation—I think those are mistakes. I think you just go with it and have fun. I like to feel it.”

The Vancouver International Mountain Film Festival takes place from February 21 to March 1. More information is at www.vimff.org/.