This impressive, often gripping documentary investigates what appears to have been a conspiracy to conceal the number of attacks, several of them fatal, made by captive orca whales on their trainers in the US, Canada and the Canary Islands. According to experts, orcas are sensitive, intelligent, socialised and not natural killers, except when turned psychotic by the conditions in which they're kept and the humiliations to which public display subjects them.Former employees of the SeaWorld chain of parks provide eloquent testimony about what attracted them to become trainers, how much they liked their work, why they've resigned and now applaud the present (but contested) ban on humans performing with the animals.