The shipbuilding feature Leonardo da Vinci proposed to help a vessel survive hull damage was a double hull.
Leonardo studied vessels with two layers of hull structure, creating a space between the outer and inner surfaces. This arrangement could provide additional protection if the outside of the ship was pierced. It also reflects Leonardo’s interest in compartmentalization and damage control in naval design.
A double hull is not the same as a double-ended ship or a ship with two separate hulls, such as a catamaran. In a double-hull arrangement, the protective layers belong to one vessel and are separated by an internal space.
Modern tankers and some other ships use double hulls for safety and environmental protection. Leonardo’s Renaissance proposal did not create the modern tanker standard, but it anticipated the value of separating cargo or interior spaces from the outer shell.