Leonardo da Vinci designed a double hull intended to improve a ship’s resistance to sinking.
The concept placed an additional layer inside the outer hull, creating a separated structure that could offer protection if the exterior were damaged. Leonardo was interested in ship safety as well as naval warfare, and his notebooks contain numerous studies of vessels, hull shapes, pumps, and water movement.
A double hull does not make a vessel unsinkable. Its purpose is to provide another barrier against flooding, a principle later used in various forms of ship construction. Modern tankers and passenger vessels may use double-hull arrangements, but their materials, compartments, and safety rules are far more advanced than Leonardo’s Renaissance proposal.
The design is sometimes confused with a catamaran, which has two distinct hulls arranged side by side. Leonardo’s proposal is better described as an inner and outer hull structure.