What ship feature did Leonardo da Vinci propose to improve watertightness?

Leonardo da Vinci proposed a double hull to improve a ship’s watertightness.

Leonardo’s ship studies include arrangements in which an inner hull is separated from an outer hull. The space between them could provide additional protection if the outside of the vessel were damaged. This is the same broad safety principle later used in some ships and especially in modern tankers.

The idea belonged to Leonardo’s wider interest in naval engineering. He studied hull forms, propulsion, water resistance, and methods for moving vessels. A double hull would add weight and construction complexity, so it was not a simple improvement suitable for every Renaissance ship.

Modern double-hull ships use carefully engineered compartments, structural members, and standards developed through naval architecture. Leonardo’s sketch should therefore be understood as an early conceptual proposal, not the origin of the complete modern tanker design. Its importance lies in recognizing that separation between outer and inner surfaces can limit flooding.