A catamaran ("cat" for short) is a multihulled vessel consisting of two parallel hulls of equal size.A catamaran is geometry-stabilized, that is, it derives its stability from its wide beam, rather than having a ballasted keel like a monohull. Being ballast-free and lighter than a monohull, a catamaran can have a very shallow draught. The two hulls will be much finer than a monohull's, the reduced drag allowing faster speeds. A sailing multihull will heel much less than a sailing monohull, so its sails spill less wind and are more efficient. The limited heeling means the ride may be more comfortable for passengers and crew, although catamarans can exhibit an unsettling "hobby-horse" motion. Unlike a self-righting monohull, if a gust causes a sailing catamaran to capsize, it may be impossible to right the multihull; but having no ballast, an upturned catamaran will be unlikely to sink.A catamaran's two hulls are joined by some structure, the most basic being a frame, formed of akas. More sophisticated catamarans combine accommodation into the bridging superstructure. Catamarans may be driven by sail and/or engine. Originally catamarans were small yachts, but now some ships and ferries have adopted this hull layout because it allows increased speed, stability and comfort.The catamaran concept is a relative newcomer for Western boat designers, although they have been used since time immemorial among the Dravidian people, in South India. Catamarans were developed independently in Oceania, where Polynesian catamarans and outrigger canoes allowed seafaring Polynesians to voyage to the remotest Pacific islands.In recreational sailing, catamarans and trimarans initially met some skepticism from Western sailors versed in traditional ballasted monohull designs.