catamaran, 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.

Twin-hulled sailing and engine-powered boat. Its design was based on a raft of two logs bridged by planks used by peoples in the Indonesian archipelago, Polynesia, and Micronesia. Up to 70 ft (21 m) long, early catamarans were paddled by many men and used for travel, in war, and in recreation. Especially after the sail was added, voyages as long as 2,000 mi (3,700 km) were made. In the 1870s they sailed so successfully against monohulled boats that they were barred from racing. The modern catamaran, which averages about 40 ft (12 m) in length, has been produced since 1950. They are very fast craft, achieving speeds of 20 mph (32 kph).

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