 The Union Navy experimented with submarines before the Confederacy produced its famed CSS "Hunley"; the result, USS "Alligator" failed primarily because of lack of suitable targets.Building on Confederate designs, the Union Navy produced and used torpedo boats, small vessels that mounted spar torpedoes and were forerunners of both the modern torpedo and destroyer type of warship.Because of haste in their design and construction, most of the vessels taken into the U.S. Navy in this period of rapid expansion incorporated flaws that would make them unsuitable for use in a permanent system of defense.