Leonardo da Vinci developed a catamaran concept using two parallel boat hulls to improve stability.
His notebooks include studies of boats and watercraft with twin hulls connected by a platform. Separating the buoyant hulls gives the craft a wider base of support than a single-hulled boat. That arrangement reduces rolling and can provide a stable working surface on the water.
The word catamaran comes from a Tamil term referring to a boat made from joined logs, and twin-hulled craft existed long before Leonardo. Therefore, Leonardo should not be credited with inventing the general idea of multihull boats. His drawing is an early European design study showing how the configuration could be applied systematically.
Leonardo also investigated paddle wheels, screw propulsion, and other marine mechanisms. Those are separate concepts, not parts that must be included in every catamaran. The defining feature here is the pair of parallel hulls, connected so they act as one vessel.