Impossible Naval Engineering

S5, E2: Naval engineering has led the way in technological advances through all History. For the simple reason that if anything goes wrong at sea, you're dead. Relive the most extraordinary Naval ambitions of antiquity. The macabre collapsible death-yacht, commissioned by Roman emperor Nero, as a one- time-only assassination device--designed to kill his own mother. The ship that needed no engine and powered up-river by itself. The underwater booby trap defense system that smashed through pirate hulls in 15th century Italy. The chemical bomb fire ships that killed hundreds on the high seas of ancient Greece. And in a high adrenaline investigation, for the first time on television, we build and test the oldest white-water rapids crafts ever discovered.