LIKE many people in his generation, Louie Psihoyos was a landlubber who grew up watching “Flipper” and Jacques Cousteau adventures on television. After National Geographic magazine hired him straight out of college as a staff photographer, his admiration for the intelligence and beauty of dolphins, and for the oceans as an ecological system, grew as he learned how to dive and began to work underwater.

But none of that quite prepared him for the experience of making “The Cove,” an award-winning documentary about the clandestine slaughter of dolphins in Japan that opens July 31. The film is the first that Mr. Psihoyos  “rhymes with sequoias,” he said  has directed, and everything about it has been a challenge, from having to make the transition from still photography, to the subject matter itself, to the cloak-and-dagger techniques used to obtain images that range, as Mr. Psihoyos put it, “from the heartbreakingly beautiful to the heartbreakingly sad.”

“The Cove,” in other words, is an unconventional documentary, one that looks very much like a feature film, with the dramatic arcs and suspense one would expect in a James Bond or Hollywood action movie. And because the film contains graphic images of the mass killing of a species of animal that humans regard fondly, with images as unsettling as those of baby seals being clubbed to death in Canada, it seems destined to generate an emotional and contentious debate.

Which is exactly what Mr. Psihoyos, 52, had in mind when he began filming “The Cove” in 2005. “What I set out to do was not so much make a movie as to create a movement,” he said by telephone from his office in Boulder, Colo. “This movie is a tool to shut this thing down and end the barbarism we saw back there in that cove.”