Leonardo da Vinci proposed a double hull to reduce damage from collisions.
His ship studies included the idea of building an inner hull inside an outer hull. If the outside layer were breached, the second layer could help keep water away from the vessel’s interior and preserve buoyancy. The principle is similar to the compartmentalized protection used in later shipbuilding.
Leonardo’s notebooks contain many maritime designs, including boats, pumps, paddle mechanisms, and naval devices. They were part of his broad investigation of fluids and machines rather than a single completed ship project.
A double hull is not the same as a double-ended ship or a ship with two separate hulls, such as a catamaran. The term means two hull layers surrounding a protected space. Modern oil tankers use double hulls partly to reduce pollution after grounding or collision, although the feature does not make a ship unsinkable. Leonardo’s proposal is an early recorded example of this protective engineering idea.