There was a time when submariners went to sea knowing that if disaster struck, they were likely never coming home. In the early days of the Silent Service, a sunken submarine was a steel tomb. Rescue was often impossible. Escape was unheard of. The ocean was merciless, and technology had not yet caught up to the bravery of the men who dared to ride beneath the waves. That is what made the invention and testing of the Momsen Lung on May 8, 1929, such a watershed moment in naval history. It was a turning point in the age-old struggle to wrest survival from the deep.