They land on beaches, transporting troops and equipment for combat. They glide hundreds of feet below the water’s surface, providing security to a hospital ship on a humanitarian mission. They include nuclear-powered Nimitz-class aircraft carriers, the largest warships in the world; 49-foot Deep Submergence Rescue Vehicles; Arleigh-Burke class-guided missile destroyers; and high-speed landing craft. They are the vessels of America’s Navy.