Thirty-five years ago, Richard O’Barry popularized dolphins, training (and living with) the bottlenose females who played Flipper on TV. Now, Louie Psihoyos’ documentary follows O’Barry’s efforts to undo the damage Flipper caused: an industry in Taiji, Japan, dedicated to capturing and selling dolphins to theme parks, zoos and illegal tanks (and killing the leftovers). To expose the industry’s hidden cove, he and Psihoyos become ecowarrior spies, hiring free divers to plant microphones under the water and Industrial Light and Magic to hide cameras in rocks while evading the paid-off police who know damn well why they’re there. What goes down is legitimately suspenseful, and when the group gets the footage they want (but can barely stand to see), we’re gutted. But writer Mark Monroe has skillfully made this story even bigger than a mass slaughter—it’s about geopolitics, cultural heritage, poisoned food and most-of-all, activism. Here, O’Barry is framed as one of a dying breed of activists willing to put more on the line than a signed Internet petition. He’s committed to the cause and unafraid of arrest. In the documentary’s final scenes, he barges into a private meeting broadcasting his Taiji footage from a TV strapped to his chest, holding his body firm as security hustles him out and we struggle not to cry.