Leonardo da Vinci proposed a double hull as a ship-protection design against flooding.
His sketches show an inner and outer hull separated by a space. The concept was intended to keep a vessel afloat if the outside shell were damaged. This is an early example of Leonardo applying practical observation and structural design to naval engineering.
Leonardo studied ships, canals, locks, pumps, and other water-management systems while working in Renaissance Italy. His maritime drawings often combine artistic perspective with mechanical details, although many remained designs rather than completed machines.
A double hull is not the same as a reinforced keel or a watertight deck. Modern tankers and passenger ships use double-hull construction for related safety reasons, but Leonardo’s drawing was a Renaissance proposal rather than a modern commercial vessel.