An investigative report on Sea World that feels like an extended segment from “60 Minutes” or its ilk, Gabriela Cowperthwaite’s documentary is a repetitive but still compelling piece of activist filmmaking about the wisdom of keeping orcas, so-called killer whales, in captivity for use in water shows. The argument is presented in both practical terms—as a safety issue regarding the staff who interact with them—and ethical ones—whether it’s appropriate to confine creatures whose brains are in some respects more developed than our own in an unnatural, and some will argue simply inhumane, environment. As is often the case with such films, “Blackfish” is also one-sided, though that’s not entirely the director’s fault, since Sea World representatives refused to be interviewed.

The film begins with footage of a recent episode that has become notorious through coverage on the news—the death of trainer Dawn Brancheau at the Orlando Sea World in 2010. It then goes into the past to argue that for some forty years the industry has not only disrupted the existence of the whales by capturing them and violating their normal familial life, but has systematically suppressed the truth about incidents in which they have turned violent in captivity. It does so by using plenty of clips from news reports, but also interviews with past employees and patrons as well as marine experts, to which are added establishing footage and a sober narration.

The story begins with an affecting scene in which John Crowe, a diver employed some forty years ago to capture orcas in the waters off Washington State, recalls how the team targeted young whales that were seized as their mothers wailed, and how the corpses of orcas that died in the course of the process were weighted down and submerged. It then proceeds to feature two witnesses to an attack on a trainer during a show at a park called Sea Land in 1991, which involved a whale called Tilikum. Yet that whale was simply shipped to another facility, and has been implicated in other incidents since, culminating in Brancheau’s death. The contention is that Sea World executives have regularly minimized the cruelty of the conditions in which the whales are kept and soft-pedaled the danger they pose to staff and patrons in order to protect the bottom line.

Cowperthwaite makes her case convincingly, citing other incidents in which trainers were badly mauled—scenes that are captured in grainy footage—and a recent episode in which a young man was found dead in a whale tank, the details of which, she argues, park officials have manipulated in order to protect their business interests. She ends by returning to the Brancheau tragedy, contending that Sea World has employed similar tactics to downplay how it reveals their operation’s systemic problems. And the film points out that those problems are hardly confined to one or two parks, emphasizing how the industry has gone global in a segment involving a Spanish venue that Sea World’s staff were instrumental in getting underway—and where troubling incidents have occurred. The film closes with court findings resulting from Brancheau’s death that nonetheless leave the central issues it revealed in limbo.

“Blackfish” is unabashedly agenda-driven, and it sometimes allows its makers’ emotion to overwhelm its sense of journalistic decorum. One might also observe that, given the way in which businesses of every sort have been caught suppressing or shading facts in order to protect their financial interests, its sense of outrage is the equivalent of Captain Renault’s expression of shock that gambling is going on at Rick’s—and that Cowperthwaite’s indictment could easily be extended to zoos and animal preserves of all kinds. But if the film helps only to increase public awareness about the treatment of whales and similar creatures in places like Sea World—and perhaps affect their bottom line in doing so, the only thing that might ultimately bring salutary changes—it will serve a useful purpose.