The images are impressive, as you’d expect in any new nature doc about the giants of the sea.

But the behaviors observed and revelations about whale “language,” “culture,” knowledge passed-down, generation to generation, expressions of curiosity, “love” and “grief” are what’s eye-opening in “Secrets of the Whales,” coming to Disney+ on Earth Day, April 22.

Beautifully photographed by whale photographer/experts like Brian Skerry, poetically put-together, written and directed by Brian Armstrong and Andy Mitchell, with Sigourney Weaver sympathetically narrating it, “Secrets” is a singularly impressive nature doc series, on a par with the best of the BBC and Disney Nature.

Orcas, belugas, humpbacks and others are highlighted over four episodes, each shown in the corners of the world where they hold forth, each distinct in its culture, songs, genetic memory and tradition and skills passed on. It took four years and trips from Alaska to Antarctica, Patagonia to the Falklands, Norway to New Zealand to film it.

“Bubble net feeding” is passed down, generation to generation, by some pods of humpbacks. Some have figured out ways to amplify their globe-girdling songs by bellowing into coral reefs, “like an amphitheater.” Only in Patagonia have orcas learned to pluck sea lions off the beach. Only in New Zealand has this one pod mastered catching sting rays, holding them upside down “which puts them to sleep,” the mother of the pod sharing her catch with her extended family.

The kid-friendly prose can tilt towards the cute, with humpbacks vying to be “the singing sensation of a hidden world.” A trip by belugas to Cunningham Inlet in Canada “is like a family trip to the spa,” where “the gravelly bottom (of the river) is like a loofah for an itch they’ve been waiting all year to scratch.”

But with just enough experts weighing in on the new “secrets” that are coming out — matriarchal orca pods, non-family herring and krill-hunting humpback parties that gather in the same places to team up, year after migratory year, belugas “may even give themselves names” — with a generally upbeat tone (photographer-divers free an orca wrapped in cables that drag fishing nets), “Secrets of the Whales” makes a great escape from the generally glum environment news piling up like “overdue” invoices all over the world.

MPA Rating: TV-PG

Cast: Narrated by Sigourney Weaver, featuring Brian Skerry and others.

Credits: Written and directed by Brian Armstrong and Andy Mitchell. A National Geographic/Disney+ release (premiering April 22)

Running time: Four episodes @ :50 minutes each