Leonardo da Vinci proposed a double hull as a protective ship design.
His maritime studies included the idea of placing one hull inside another, creating a space between the outer and inner structures. Such separation could help protect the vessel from damage caused by collisions or attacks.
The concept is important because it anticipates a principle later used in ship construction. Modern double-hull tankers place cargo tanks inside an outer hull, reducing the chance that a collision will directly rupture the cargo tanks.
Leonardo’s proposal was not a modern tanker design, and he did not build a full-scale double-hulled ship. His notebooks contain many maritime inventions and observations, including ideas for boats, diving equipment, and mechanical water devices.