Gabriela cowperthwaite had long considered trips to SeaWorld San Diego with her twin boys a good parent's duty. Who doesn't love Shamu? Then in February 2010, an experienced trainer at SeaWorld Orlando, Dawn Brancheau, was killed by an orca named Tilikum, who drowned her and tore her body apart in front of horrified families. "I couldn't understand how Dawn Brancheau came to be killed by an animal that we consider to be our friend," Cowperthwaite tells me.
That question is at the heart of her new film, Blackfish. At first Cowperthwaite believed Brancheau's death was an anomaly. But Tilikum, now estimated...