What Leonardo da Vinci design used two hulls to improve a ship's safety?

Leonardo da Vinci designed a double-hull ship concept with two parallel hulls for added protection against leakage.

The idea appears among Leonardo's studies of watercraft and naval engineering. Separating the vessel into two hulls could provide greater stability and create a protective arrangement if one side was damaged. His broader ship designs also explored propulsion, steering, and ways to reduce resistance in water.

Leonardo's drawing is an early example of thinking about hull redundancy, although it was not a modern tanker's double hull in the legal or industrial sense. The concept was not built as a documented Leonardo vessel, and no ship from his workshop is known to have used it.

Modern double-hull ships have an outer shell and an inner cargo boundary with a space between them. That arrangement is especially associated with reducing oil spills after collisions or groundings. Leonardo's sketch belongs to the much earlier history of experimental naval design, not directly to modern maritime regulation.