Filmed for IMAX 3-D screens, this ocean documentary follows creatures that rarely appear in nature films: giant Pacific octopuses changing color and texture in seconds, sea nettles drifting in slow motion, and predators like sharks and killer whales working the open water in search of prey. Cameras follow a mother sea otter teaching her pup to dive and a colony of seals navigating a kelp forest, alongside the tiny plankton and larval fish that feed the whole system from the bottom up. The footage moves from sunlit reefs to darker, colder water where bioluminescent animals generate their own light. Narration frames the ocean as a single connected system, tracing how a change at one level, a drop in plankton or a warming current, moves through the food chain to affect whales and seabirds far from where it started. Built for the large-format screen, the film relies on close, patient camera work rather than narration to make its case for what is actually down there.