The Navy League's Sea-Air-Space Exposition is the largest maritime expo in the U.S., and brings together dozens of defense contractors and military decision-makers. The Motley Fool's Rex Moore was at the event in National Harbor, Maryland, and saw demonstrations of several technologies. In the video below he shows us how General Dynamics (GD -0.47%) is increasing the capability of U.S. submarines, including new ways to launch and recover the Lockheed Martin (LMT -0.97%) autonomous underwater vehicle.