A documentary by Luke Cresswell and Steve McNicholas. Rated G.

African elephants, mountain gorillas, great white sharks, maybe, but the lowly sardine as the star of an IMAX creature feature? It’s a lot more fascinating than it sounds, and the humble fish’s role in one of the last great natural ocean phenomena helps make this one of the most fulfilling giant-screen flicks in years.

Wild Ocean 3D has it all: the breathtaking scenery of South Africa’s KwaZulu-Natal Wild Coast; an urgent message about sustainable fishing; and as much care put into depicting the people who live along the coast of the water as the stunning creatures who swim below it. Don’t let the 3-D glasses fool you: this is an artful production driven by indigenous music.

But back to the sardines. Anyone who has seen Finding Nemo knows they move in a huge, silvery “bait ball” to fool their predators. Trust me, it’s much more impressive stretched across a giant IMAX screen, with dolphins, black-tipped sharks, and penguins slicing through the glittering, undulating masses.

Each year, like clockwork, there’s a literal feeding frenzy in the waters off South Africa’s eastern coast, where raging waves shatter against red cliffs. As striking aerial footage shows, massive, oil-slick-like groups of sardines move into the area, followed by the shadows of their large predators. The free-for-all isn’t just happening below the surface; villagers gather with nets, long fishing poles, and even upturned skirts to get in on the action.

That’s where the bad news comes in. As thoroughly explained in the film, this last unbroken food chain is threatened due to warming oceans, overfishing, or both. Without lecturing, Wild Oceans becomes a surprisingly impassioned cry for marine reserves—at least for a movie that you watch while wearing plastic cartoon spectacles.