catamaran (kătˌəmərănˈ) [key], watercraft made up of two connected hulls or a single hull with two parallel keels. Originally used by the natives of Polynesia, the catamaran design was adopted by Western boat builders in the 19th cent. Because the twin hulls of the Polynesian catamaran are actually logs or other pieces of wood, the vessel is more like a raft than a boat. An extremely stable craft, it can be paddled or sailed even in the heavy waves of the S Pacific. The American Nathanael Herreshoff first built Western-type catamarans in the 1870s. The twin-hulled sailing or motor boat has since become a popular pleasure craft, largely because of its speed and stability. High-speed catamaran ferries can exceed 40 knots (74 km per hr). Catamarans range from 12 ft (3.7 m) to 315 ft (96 m) in length and are among the world's fastest sailing and motor craft.