Leonardo da Vinci proposed a double hull as a protective shipbuilding feature against underwater damage.
The idea placed an additional layer of structure inside the outer hull, creating a buffer between the sea and the vessel’s interior. If the outer skin were breached, the second layer could reduce the chance that water would immediately flood the ship. Leonardo considered the concept in the context of naval engineering and ship safety.
A double hull is not the same as a watertight bulkhead. A double hull creates a protected space along the vessel’s bottom or sides, while bulkheads divide the interior into separate compartments. Modern tankers and some other vessels use double-hull construction for safety and environmental protection, but Leonardo’s Renaissance proposal was not a modern regulated ship design. It is best understood as an early conceptual contribution to layered marine construction.