The Global Ocean. The episode is set in the only ocean in the world, 200 million years into the future. At this point in the future, there are no mammals, birds, reptiles or amphibians. The episode focusses on four species: (1) Rainbow Squid, a massive squid which changes colour to hide and which did not take to the land unlike some cephalopods; (2) Ocean Flish, descendants of cod which have evolved to breathe out of water and have developed wings; (3) Sharkopath, a descendant of sharks that have bioluminescent patches on their sides to communicate with one another; (4) Silverswimmer, descendants of crustaceans that have grown in size and evolved to fill the roles that fish previously held.