Shows how a submarine works. Explains how it surfaces, moves, floats, and dives. Goes on board a giant Trident submarine. Describes its various parts: engine room, missile forest, control room, mess (cafeteria), kitchen, torpedo room, crew quarters, bridge, library, and computer training center. Explains how crewmen learn how to operate submarines at the Trident Training Facility. Tells how submarines help scientists learn about life deep in the ocean. Also includes a brief history of submarines, the different types of submarines, and nautical vocabulary.