The ocean is the last frontier -- The ocean is full of extremes -- Research ships are floating laboratories -- Submersibles go deeper than ever -- Divers can explore shallow depths -- Observation systems monitor the oceans -- Strange creatures live in the deep ocean -- Shipwrecks litter the deep -- Underwater volcanoes change earth's surface -- Underwater cities, the past and our future -- Ocean currents are a possible energy source -- The SeaOrbiter is an oceangoing spaceship.