Leonardo da Vinci proposed a double hull to make ships more resistant to leaks and damage. His notebooks include the idea of placing two layers of hull structure around the vessel.
A double hull creates an additional barrier between the water and the interior of the ship. If the outer layer is breached, the inner layer can help keep the vessel afloat. Leonardo’s proposal therefore addressed survivability and structural protection rather than propulsion or navigation.
The idea is often confused with a double-ended ship or a reinforced single hull. A double hull specifically means two hull layers separated by a space or structural arrangement. Modern ships may use double hulls for different safety purposes, including oil-spill prevention and protection against collisions.
Leonardo’s naval studies also considered paddle propulsion, ship design, and hydraulic engineering. His double-hull concept was not a modern steel tanker design, and the surviving evidence concerns a proposed construction principle rather than a documented Leonardo-built vessel.