Leonardo da Vinci proposed a double hull to improve a vessel’s resistance to damage.
His naval designs included an inner and outer shell separated by a space. If the outer hull were breached, the inner hull could help keep water away from the ship’s interior. This is the same broad protective principle later used in some modern ships and submarines.
Leonardo’s proposal belongs to his wider studies of boats, shipbuilding, buoyancy, and naval engineering. He often explored how layered structures could add strength or provide protection without relying on a single wall.
A double hull is not the same as an outrigger, which is a lateral float used to increase stability, or a raised deck, which changes the ship’s upper structure. Leonardo’s design was specifically about separating two hull surfaces. Modern double-hull tankers use the arrangement mainly to reduce pollution after collisions or groundings.