Leonardo da Vinci proposed a double hull as a way to reduce the danger of flooding.
A double hull places two watertight layers around a vessel, creating a space between the outer and inner structures. If the outer layer is damaged, the inner hull can still protect the ship’s compartments and buoyancy. Leonardo’s notebooks contain designs for a ship with this kind of layered protection.
The idea belongs to his broader work on military and naval engineering. He studied ship construction, waterways, locks, pumps, and methods for moving vessels. His proposals were inventive, but many remained drawings rather than completed machines.
Double hulls later became important in shipbuilding, especially for tankers and passenger vessels. They are not the same as catamarans, whose two hulls are separate side-by-side bodies designed to support a deck and influence stability.