We're in a submarine at the DEEP campus, the company on a mission to get people to live underwater for months at a time, by the end of this decade, in one of these habitats. We'll take you underwater in a submarine to see where the habitats will first be tested. Then we'll go inside Sentinel – one of the two habitats DEEP is currently developing, and explore the history of the technology, as well as what it could mean for the future of deep sea exploration.This small lake is actually an old limestone quarry ...