In the second episode, Will Smith descends 3,300 feet to the bottom of the ocean in a deep-water submersible, where even fewer people have gone than outer space. Along the way down, Will and explorer Diva Amon investigate how colour is used in the natural world and the role of bioluminescence. In the oceans, nearly 80 percent of animals use bioluminescence in some way, possibly the most common form of communication on the planet.