Leonardo da Vinci proposed a double hull to make a ship less vulnerable to leaks.
A double hull places a second layer of hull structure inside the outer shell, creating a space between them. If the outer skin is damaged, the inner layer can help keep water from reaching the vessel’s interior. Leonardo included a related ship design in his notebooks, showing an early understanding of layered protection against flooding.
The concept was not a complete modern naval specification. Leonardo did not establish the detailed compartmentation, materials, pumping systems, or construction rules used in later ships. His proposal belongs to a wider body of Renaissance naval engineering that included paddle wheels, specialized boats, and underwater devices.
Double hulls later became important in shipbuilding and marine safety. Modern tankers use them to reduce the chance that a collision or grounding will breach cargo tanks directly. The same general principle also appears in some submarines and other vessels, though their structures and safety requirements differ from Leonardo’s early concept.