The adoption of nuclear power revolutionized submarine design and means that vessels can stay underwater for months, trailing the enemy or training weapons on land targets from secret positions, “always there, never seen.” Jim Christley, a former submariner, explores here the influence of Admiral Hyman Rickover in cautiously introducing these stealthy machines of war, and frankly discusses the power and perils of using nuclear reactors at sea. Using unique and detailed artwork, he outlines the many evolving aspects of design within the submarine classes, from the very first nuclear submarine, USS Nautilus, to the classes under construction even now.