What Leonardo da Vinci invention used two linked hulls to improve a boat's stability?

Leonardo da Vinci designed a double-hull boat concept intended to improve stability on water.

The design used two parallel hulls connected by a deck or framework. Separating the buoyant sections creates a wider base of support than a narrow single hull, reducing side-to-side rolling and making the craft more stable.

This arrangement resembles the principle used by modern catamarans, although Leonardo's sketch should not be confused with the complete history of multihull boats. Double-hulled watercraft existed in several maritime cultures long before the Renaissance.

Leonardo studied boats, canals, locks, and other hydraulic technologies throughout his career. His double-hull concept was part of that wider interest in improving transport and engineering on water, not evidence that he invented every form of catamaran.