Director Gabriela Cowperthwaite puts together a compelling argument against keeping killer whales in captivity in Blackfish.

The No. 1 argument: the death of head Sea World trainer Dawn Brancheau in 2010, killed during a non-show exercise by Tilikum, one of the amusement park’s star-attraction killer whales. Trainers and friends of Brancheau recall, in chilling detail, how Brancheau died—and the extent of her injuries are a shocker. She didn’t simply slip into the tank and get dragged under by her hair, as Sea World first claimed: She suffered many, horrible injuries in the mouth of the whale.

Tilikum has been involved in three human deaths while in captivity, including one at another, smaller park. It’s sad to hear the stories about this majestic, sometimes-placid creature basically losing his mind in captivity.

There’s also stunning footage of a 2006 incident in which a whale seemed determined to drown its trainer, taking him to the bottom of the pool numerous times during an extended incident. The film covers other deaths as well.

Blackfish is a blistering indictment of Sea World’s practices. Clearly, trainers shouldn’t be allowed to swim around in tanks performing tricks with these whales, a practice currently legally banned at Sea World (a fact Sea World execs continue to protest).

Hopefully, this film will lead to further steps—including the stoppage of killer whales being used for the purpose of amusement.

Special Features: There’s a director’s commentary, and some unused segments, including one about excessive damage to a whale’s teeth during captivity, and another featuring a former trainer talking about his positive experiences with whales.