Leonardo da Vinci proposed a double hull, placing two protective layers around a ship.
The concept gave a vessel an outer shell and an inner hull separated by a space. Such separation could help protect the interior if the outer layer were damaged. Leonardo’s maritime notes explored ways to improve ship strength and safety, reflecting his broader interest in watercraft, buoyancy, and structural engineering.
A double hull is not the same as a watertight bulkhead. A bulkhead divides the inside of a ship into compartments, while a double hull adds a second shell around the vessel. Modern ships use double-hull construction for particular safety purposes, including reducing the chance that an impact will immediately breach cargo tanks. Leonardo’s proposal was an early conceptual example, not a modern regulated shipbuilding system, and it was not known to have been implemented as a working vessel during his lifetime.