The ocean covers roughly seventy percent of the Earth's surface, and this four-part series works through what lives in it, layer by layer. It starts small, with plankton, the microscopic organisms that form the base of nearly every marine food web, and builds outward to the animals at the top of it: sharks, tuna, and other fast aquatic predators built for hunting in open water. Episodes move between sunlit shallows and the deep sea, where pressure, cold, and darkness shape animals that rarely surface in other wildlife films. The series treats the ocean as one connected system rather than a set of separate habitats, tracing how energy and nutrients move from plankton blooms up through the food chain to the largest hunters. Footage covers reef, open ocean, and deep-water environments, with the focus staying on how these zones depend on each other rather than presenting each as an isolated spectacle. It's a straightforward survey of marine ecology across four episodes, built to cover breadth rather than dwell on any single species.