Leonardo da Vinci sketched a double hull using two layers of ship structure. The space between the layers could provide additional protection against damage and help keep water from entering the vessel after an impact.
The concept appeared among Leonardo’s maritime studies, which included ships, canals, pumps, and methods for controlling water. A second hull would add weight and construction complexity, but it could make a vessel more resistant to puncture. This principle later became important in ship design and maritime safety.
Leonardo’s sketch should not be confused with a modern oil tanker built to contemporary double-hull standards. His drawing was a design proposal rather than evidence that he constructed a full-size ship using the arrangement. Modern double hulls are carefully engineered with ballast spaces, structural frames, and regulations governing their dimensions and use.