Leonardo da Vinci proposed a double hull as a method of protecting a ship’s interior.
A double hull places one hull surface inside another, leaving a space between them. Leonardo explored this arrangement in his studies of ships and naval engineering. The inner layer could help shield the vessel’s contents from damage if the outer layer were breached.
The idea is notable because modern ship design also uses double hulls for protection, especially in oil tankers. In modern vessels, the two hulls create a separation that can reduce the chance that a collision or grounding immediately reaches cargo tanks. Leonardo’s historical concept was not a complete modern tanker specification, however.
A double hull should not be confused with a catamaran. A catamaran has two separate hulls side by side, while a double-hull ship has nested layers forming one protected vessel.