In Marineland, the sprawling aquatic park in Niagara Falls, Ontario, lives a walrus named Smooshi. Concerns for the sea mammal’s well-being form the core of the documentary “The Walrus and the Whistleblower,” which follows the former trainer Phil Demers’s fight to free Smooshi from her captivity.

Demers believes that, while he was working at Marineland, Smooshi imprinted on him, or deemed him her guardian. The director Nathalie Bibeau pairs Demers’s account with home video footage of the pair playing during off-hours at the park. At the time, a local news story about their bond spread nationally, even appearing on “Jimmy Kimmel Live.” But in 2012, after witnessing the animals suffer chemical burns, Demers quit his job and vowed to expose the park’s abuse.

As Bibeau examines the movement born out of Demers’s allegations, she hews closely to her subject. The film tracks a hefty lawsuit Marineland files against Demers, and a bill he supports that would ban the captivity of whales and dolphins in Canada. The legal and legislative battles supply narrative through-lines, but their progression — or rather, their stagnation — proves dull padding for the story.

More intriguing is Demers’s yearning for the walrus he is barred from seeing, a fixation that scans as alternately authentic and performed. Frustratingly, the documentary declines to probe Demers’s evolving relationship to his activism and newfound fame — particularly once he assumes a grandiose Twitter persona and scores repeat appearances on Joe Rogan’s podcast.

“I’m Smoochi’s mom,” Demers declares at one point. “What’s more natural than reuniting a baby with its mother?” With sharper framing, this line might suggest irony, given the unusual nature of this cross-species relationship. Offered at face value, all that registers is bombast.

The Walrus and the Whistleblower
Not rated. Running time: 1 hour 28 minutes. Watch on Discovery+.