Leonardo da Vinci proposed a double hull as a shipbuilding feature intended to improve protection from leaks.
His naval studies included the idea of placing two layers of hull structure around a vessel. The space and added material between the outer and inner surfaces could provide extra resistance to damage, especially from impacts or punctures.
The concept belongs to Leonardo’s broader work on ships, canals, pumps, and water engineering. It should not be confused with a modern double-hull tanker, whose structure is governed by later naval architecture, materials, regulations, and safety standards.
Leonardo’s drawings were proposals rather than evidence that he built a full-scale double-hulled ship. Nevertheless, the design is frequently cited as an early historical example of the double-hull principle in ship construction.