Mesmerizingly beautiful diving footage, a drifting narrative and some solid performances recommend “Blueback,” a sweet but somewhat squishy eco-parable set Down Under and starring native Oz daughter Mia Wasikowska.

It manages to tell the story of a young woman’s lifelong “friendship” with a Western Blue Grouper in the bay where she grows up, and to which she returns as a trained marine biologist trying to save coral reefs and the many species that depend on them to survive, without turning maudlin — no mean feat considering the conventions of the genre.

We meet Abby (Wasikowska) as an adult, diving on the Great Barrier Reef with a fellow researcher (Albert Mwangi), surveying the mass die-off of corals and confiding in the many fish she keeps in tanks on her research vessel.

“It’s not good news, I’m afraid,” she tells those reef fish species samples. “Your home is dying, and I don’t know how to help.”

Before she can figure out a strategy to combat rising sea temperatures and climate-change-linked pollution, she gets more bad news. Mum has had a stroke.

Traveling back to the other side of Australia to help her mother (Liz Alexander), who has lost her ability to speak, Abby rummages through her childhood drawings and her memories to try and engage her mother on a subject they both love — “our bay.”

Radha Mitchell plays Mum Dora in flashbacks from back then, a plucky and brave widowed mother who helps Abby (Ariel Donoghue) celebrate her eighth birthday by motoring into the bay and making her snorkel down to fetch the wedding ring Mom drops over the side.

“I can’t Mum, it’s too far” won’t cut it. She’s a “big girl now,” and Mom’s all about prepping her for life and passing on her love of the sea to her.

That giant fish that scares Abby when they’re free-diving for abalone? There’s nothing for it but to go back down and “meet” it.

It’s a giant grouper — curious, friendly (and not shy about stealing her abalone) and wholly settled in their bay.

“The only way to keep him safe,” Mum counsels, “is to keep him secret.”

The threat to that is the rapacious developer (Erik Thomson) who seems to figure looting the fish and crustaceans in the bay is the best way to get his planned mass development approved by the local council.

Dora, a sort of self-appointed warden of this stretch of coast and water, learns to protest and fight back, and she passes on that spirit to Abby, something the daughter brings up as part of her effort to get Mum talking again.

Eric Bana is a charming rogue of a local fisherman Mum was constantly hassling to protect the resource during Abby’s youth. And as Abby ages into her teens (played by Isla Fogg), she learns more about this corner of the world on land and sea from her Aboriginal schoolmate and first crush Briggs (Pedrea Jackson).

Briggs (Clarence Ryan) is still around when Abby comes home to care for her mother, and her mother’s pet project, “our bay.”

Writer-director Robert Connolly (“The Dry” was his, not bad) introduces a lot of story elements and possible directionsin which to take this tale. But “Blueback” seems incomplete, as if Connolly (adapting a Tim Winton book) couldn’t figure out which path to take. There’s so much concern for not becoming “cloying” that “Blueback” never amounts to what it might have.

He had the cast — Mitchell is great, Wasikowska as good as ever and Bana as colorful as you’d hope. He had the lovely diving footage and a grand grouper effect. But “Blueback” doesn’t so much reach a dramatic climax as half-heartedly conclude, with a lot of heart yet lacking a satisfying resolution to the narrative.

Rating: PG, mild peril

Cast: Mia Wasikowska, Radha Mitchell, Ariel Donoghue, Clarence Ryan, Erik Thomson and Eric Bana

Credits: Scripted and directed by Robert Connolly, based on the book by Tim Winton. A HanWay/Quiver release.

Running time: 1:42