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 0.69%) is increasing the capability of U.S. submarines, including new ways to launch and recover the Lockheed Martin (LMT -0.11%) autonomous underwater vehicle.