The U.S.S. Monitor
The U.S.S. Monitor was by some descriptions the boat that defied reason. Many critics of the vessel thought she would never be a viable ship design and was predicted by many be an outright failure. The design was revolutionary to be sure but no one realy had a clear idea of just how revolutionary the design truly was. When she was concieved and built on the designs of John Ericsson in under 100 days at the Continental Iron Works located in Greenpoint, NY. She was unique in all aspects of her construction.
The most significant of those, was the revolving turret which housed to two smooth bore Dahlgren guns. The idea of a turretted gun existed before this application for the defense of military ground installations. Ericsson is the first to actually apply it to a vessel. The idea is revolutionary in its application because this allows the guns to be trained on the enemy without having to manuever the vessel. Additionally Ericsson designed a two ram steam system for rotating the turret, another of his patented ideas. A huge advantage in battle, broadsides for the Monitor were a thing of the past. The rule book of naval engagements was suddenly irrelevant. The U.S.S. Monitor was about to rewrite it.
Another novel concept applied to the Monitor was the limited amount of freeboard. Freeboard is the amount of the vessel exposed above the water line. The Monitor was innovative because the freeboard was averaged two feet. While this doesn't seem to be a siginificnt factor, it greatly reduces the cross sectional target for the enemies cannon shot. Contemporary frigates and ships of the line had tremendous amounts of freeboard to maximize the number of guns the ship could carry. Multiple decks means more cannon but it also means bigger target. In the case of the Monitor cannon shot if it hit the deck would simply reccochet off leaving the vessel unharmed.
Of course the advantage of limited freeboard comes with a cost of limited sea worthyness. While the Monitor was being towed by the U.S.S. Rhode Island. A gale blew up and the swells began to build. The Monitor had been prepped for the ocean voyage with additional packing around the turret but it was of no consequence, the waves were to big and the packing was to no availe. The Monitor sank on Dec 31st 1862 in 230 ft of water off the coast of Cape Hatteras. 16 of the crew were lost but most of hte men were saved by the brave Rhode Island.