A documentary by Rob Stewart. Rated PG.

As the director, narrator, and star of Sharkwater, Rob Stewart is on a mission. The rookie documentary filmmaker wants us to understand that the shark is misunderstood. Along the way, he hopes to slow down the slaughter of the shark population. (The black market for the creature's fins for shark-fin soup, a culinary status symbol in China, has helped deplete the shark population by 90 percent in the past 50 years.) Challenging the image of the shark as a predatory monster with an insatiable craving for toe- and finger-fringed appetizers is a tall order. Luckily for the fish, Stewart may be the world's most passionate shark geek.

Armed with the sobering testimony of experts and an impressive array of statistics, Stewart puts forward a solid ecological argument linking the destiny of sharks to our own survival. We learn that sharks are vital to the precise balance of marine life that inevitably sustains humanity. We also learn that they're genuinely afraid of humans. Stewart calls the occasional attacks on swimmers "shark mistakes"—the result of their senses getting screwed up or them mistaking our bodies for the shape of a struggling seal. "More people are killed by pop machines than sharks," he says.

Stewart's approach to his subject matter is greatly aided by the breathtaking footage he's managed to accumulate over the past four years. After decades of practice, he's learned to move among sharks so they aren't frightened by his presence. As a result, we see him happily swimming among them and—in one mind-boggling moment—cradling and petting a smaller shark as if it were some sort of underwater puppy.

It's not hard to imagine Hollywood taking advantage of Stewart's movie-star looks and coming up with a revamped blockbuster called The Shark Whisperer. As it is, the documentary includes dramatic battles with everything from corrupt officials to flesh-eating disease—not to mention the time the filmmaker spent with eco-warrior Paul Watson, whose attempts to stop shark-poaching in Costa Rica backfire with heart-racing results.

Stewart deftly manages to destroy a lot of the harmful mythology surrounding the shark. Still, the common sense that drives Sharkwater may not be enough. As one expert in the film notes, humans have a need to assign a definite shape to their deepest fears. And for a lot of us, that shape has big teeth and a dorsal fin.