Unapologetically designed both to inform and affect, Gabriela Cowperthwaite’s delicately lacerating documentary, "Blackfish," uses the tragic tale of a single whale and his human victims as the backbone of a hypercritical investigation into the marine-park giant SeaWorld Entertainment.

Denied on-camera interviews with park executives, who have strenuously taken issue with the film’s contentions in a lengthy news release, Cowperthwaite tells the distressing story of Tilikum, a 12,000-pound bull orca implicated in the deaths of three people. Through the rueful voices of former trainers and whale experts, a narrative driven by disillusion and regret unfolds as the trainers point to a gap between SeaWorld’s public image and behind-the-scenes reality.

‘BLACKFISH’ Rated: PG-13 Opens today at Kahala 8

Seemingly supported by chilling video and the oral testimonies of two witnesses to Tilikum’s first attack in 1991, the trainers accuse SeaWorld of cover-ups and misinformation.

Much of the footage is painful to watch: bleeding whales, flanks raked by the teeth of their fellow captives; a trainer crushed between two gigantic beasts with only his wet suit holding him together; another trainer dragged repeatedly to the bottom of a pool until he manages to escape.

Providing context for this alarming behavior, researchers describe highly socialized, caring creatures used to living in thousands of miles of ocean and ill-suited to theme parks where they may be subjected to repeated overnight confinements in dark concrete pens.

"If you were in a bathtub for 25 years, don’t you think you’d get a little psychotic?" Jane Velez-Mitchell, a CNN anchorwoman, wonders in a clip that’s used in the film. Other signs of mental distress, like severe tooth and stomach problems caused by the whales gnawing on their enclosures, are described.

But the film’s most harrowing moment occurs not while addressing Tilikum’s 2010 mutilation and killing of a senior trainer, Dawn Brancheau, at the park in Orlando, Fla., but in a face-to-face with a former whale hunter, the diver John Crowe.

Tearfully recalling his traumatic capture of whale calves four decades ago in Puget Sound while their mothers howled pitifully ("We were only after the little ones"), Crowe seems haunted to this day by the unearthly sound of the animals’ apparent grieving.

Calmly and methodically countering SeaWorld’s contention that whales benefit from captivity — the website "Orcas in Captivity" places the current total at 45 — Cowperthwaite questions the advisability of exploiting mammals whose brains, the neuroscientist Lori Marino suggests, may be more complex than our own.

"When you look into their eyes, you know somebody is home," one of the trainers says. Perhaps that’s why SeaWorld’s most well-known show was called "Believe."

———

Review by Jeannette Catsoulis, New York Times

© 2013 The New York Times Company