Blending his directing skills and a personal passion, James Cameron trains his lens underwater to volcanic vents in the Atlantic and Pacific oceans, where he's joined by a squad of NASA scientists and marine biologists. Part of a submerged mountain chain called the Mid-Ocean Ridge, the vents spew superheated water that serves as a haven for creatures unlike anything ever seen, including stomachless, 6-foot worms and sightless white crabs.