A canoe is a lightweight, narrow water vessel that is typically pointed at both ends and open on top. It is propelled by one or more seated or kneeling paddlers facing the direction of travel and using paddles. Canoes were developed by cultures all over the world, including some designed for use with sails or outriggers. Until the mid-19th century, the canoe was an important means of transport for exploration and trade, and in some places is still used as such, sometimes with the addition of an outboard motor. Canoes are now widely used for competition and pleasure, such as racing, whitewater, touring and camping, freestyle, and general recreation. Canoeing has been part of the Olympics since 1936. The intended use of the canoe dictates its hull shape, length, and construction material. Historically, canoes were dugouts or made of bark on a wood frame, but construction materials evolved to canvas on a wood frame, then to aluminum. Modern canoes are made of wood, canvas over wood frames, aluminum, molded plastic, fiberglass, or synthetic fiber composites.