Blackfish is a 2013 documentary movie about captive orcas (killer whales) at SeaWorld in Orlando, Florida. It centers on Tilikum, the infamous orca who killed three people (including two trainers) and is still at SeaWorld.  The documentary, directed by Gabriela Cowperthwaite, premiered at Sundance in Utah, and has received a lot of critical acclaim. It gets a 97% from the critics on the Rotten Tomatoes site, and Wikipedia says this:

Critical reception for the documentary has been mostly positive^, with the Deseret News calling it “a gripping example of documentary filmmaking at its finest”. Twitch Film and The Hollywood Reporter both praised Blackfish, with both review sites arguing that the film gave “a persuasive case against keeping the species – and by extension any wild animal – in captivity for the purposes of human entertainment”. Film School Rejects gave the documentary a rating of B-, writing that…