Swimming with a shiver of huge sharks with nothing in front of you but a fragile underwater camera is, as it turns out, not all that dangerous. Exposing an unregulated and illegal multibillion-dollar shark-finning industry is definitely more so. Rob Stewart showed us that in 2007 in Sharkwater, his first documentary. An even more daunting mission is taking on some of the world’s worst environmental offenders, something he does in Revolution, released in Canadian theatres in April and on DVD in August.

Apples and oranges, perhaps, but it’s a natural progression, part of the maturation of the 33-year-old Toronto native, already one of Canada’s mostlauded documentary makers. Stewart is as skilled at alarming us and grating on our consciences as he is at producing his signature jaw-dropping underwater cinematography — and like Sharkwater before it, Revolution contains plenty of both. It’s a survival guide of sorts, a showcase of a few cunning species with remarkable survival strategies. Then there’s humankind: terrifyingly shortsighted, greedy and indifferent, perpetrators of overfishing, ocean acidification, widespread deforestation and other unsustainable activities.

But humans are perpetrators of hope too, especially youth. Stewart celebrates the latter for their place outside the system, for their passion and willingness to clamour for an evolution of thought and action. The title of his recent memoir may best capture the calling of this filmmaker, once almost exclusively a shark conservationist: Save the Humans.