Prone to despair about the state of the world? The Cove could send you spiraling into a deep funk about the endless damage humankind is visiting upon the planet. Our oceans are being fished-out, chemicals render much of the food we do catch toxic, and greedy governments often favor profit over the environment. The Cove is about a lot of things, but at its most basic, it is about the determined, often brave efforts of a team of extreme activists to expose the dolphin slaughter that happens each year in the Japanese coastal village of Taiji.

The annual “harvesting” of the dolphins has two phases. In the first phase, the comely, show biz-y dolphins the Taiji fishermen capture are hand-picked by trainers and taken away to amusement parks. In the second “harvest,” the remaining dolphins are hustled out of sight, sequestered in a secret cove where outsiders and cameras never venture. In that cove, the dolphins’ violent deaths turn the sea a sickening shade of red.

The film builds toward this inevitable revelation with white-knuckle suspense as a team of activists try to document the secret, nefarious activities in the cove. In this thriller-doc, the entertainment value of a heist flick combines with the merits of a cause.

The person at the center of the effort to stop the dolphin slaughter has the zeal of a reformist. Ric O’Barry is essentially the man who introduced the world to dolphin-mania on the ’60s TV dolphin drama Flipper. He has had to live with the guilt ever since. Once he got to know the dolphin, O’Barry realized the error of his ways. “I knew they were self-aware,” he confesses to director Louie Psihoyos. O’Barry, who has the air of a man consumed by regret and anger, began a passionate crusade to release dolphins from captivity (often wielding the wire cutters and other items of commercial sabotage, himself). In The Cove, O’Barry enlists Psihoyos and his friends, a group of tan, sporty Californians in black skull caps and goatees, to expose and end the dolphin slaughter.

Unlike the steroidal soldiers in G.I. Joe, these guys are real-life action figures. Each one — a movie special effects guy, a pair of sleek, movie star-pretty deep sea divers — has a special skill to bring to the project. This is an action film for activists, with the sexiness of a Mission: Impossible-style high-tech caper. The extreme activists are not only cool, their impressive jobs in technology (an Industrial Light and Magic special effects dude creates cameras hidden inside rocks to document the cove activities) gives them access to awesome, expensive toys.

But despite the entertaining, thriller riggings of The Cove, the cynical among us may note, that while this slaughter of the most sentient and human-like of creatures is cruel and grotesque, it is just a quicker version of what awaits the dolphin one way or the other. The Cove is capable of inspiring a heaping helping of Caring Fatigue: that spasm of hopelessness that accompanies even more news that the planet is ruined and the people who inhabit it are selfish beyond belief. The dolphin that swims so joyfully and beautifully through the sea, communing with surfers and divers, saving humankind from shark attacks, is doomed no matter how you slice it: rounded up for trained animal shows to spend its lifetime caged in cement ponds or exposed to levels of mercury in the environment that renders its flesh toxic to human beings.

The Cove presents a world that has lost its grip on reality: even the Taiji fishermen who respond to the activists with taunts and bullying see no irony in their conversation before the dolphin slaughter. They trade whale stories, about the time when the oceans were teeming with the creatures as far as the eye could see. But they seem to see no relationship between their aggressive fishing of the ocean and its widespread depletion. The Cove suggests that in 40 years, we will have essentially fished out our oceans, leaving a large portion of the humankind that relies on the sea for food, in danger of starvation.

Humans have made a terrific mess of the planet, and the efforts of the environmental dream team in the otherwise rousing, admirable The Cove may be all for nothing.