Who are these men, 130 strong, confined in a steel blue tube deep in the ocean for months at a time? Surrounded by a hostile environment, in constant danger - what do they do and why do they do it? This film explores the challenges faced by those select few who are qualified to serve on such missions. The viewer visits a "wet trainer" at Sub School to see what these subamriners must endure before they ever climb inside one of these remarkable ships. Included are interviews with some of the most honoured submarine commanders, and an overview of the development and strategic use of the submarine in both world wars. Also featured is a special appearance by author Tom Clancy.