An estimated 23,000 wild dolphins are killed every year in Japan. In massive dolphin roundups, bottle-nosed dolphins are weeded out to be sold and trained as show animals, while the rest are harpooned en masse and—despite dangerously high levels of mercury in their flesh—sold in supermarkets, often mislabeled as other kinds of meat. There are no words to describe this sort of slaughter that don't pale in comparison to The Cove's footage, mercifully brief, of the ocean churning red.

But The Cove, which centers on the Japanese whaling industry (and in particular, one hidden cove in Taiji, Japan, in which thousands of dolphins are slaughtered annually), is much more than another "behind the scenes at the slaughterhouse" documentary. More than anything—and even more than as a dismaying exposé of modern-day dolphin hunting practices—The Cove demonstrates how a group of well-funded activists, mostly Americans, harnessed all the influence and high-tech gadgetry at their disposal to directly challenge the traditions of another country.

The film's impetus is provided by Richard O'Barry, a dolphin-rights activist who was once a lead trainer on the show Flipper, and who blames himself for contributing to the public's fascination with dolphins—to the idea that they're smiley, cheerful little sea clowns, happy to jump through hoops for our entertainment. O'Barry's 20-year campaign to free captive dolphins and to raise awareness about whaling practices leads him to Taiji, where whalers and local officials collude in keeping the true nature of the dolphin industry a secret.

The film's objective is to get footage from the cove where Taiji's dolphin slaughter occurs—so O'Barry and his friends enlist the help of divers, Hollywood set makers, and more to stage a guerilla filming operation. They get their footage. It's horrifying. It's also exhilarating, nerve wracking, thought provoking, moving, and inspiring. In short, it's everything a documentary should be.