what is a raft

A raft is a flat structure used for support or transportation over water. It is usually of basic design, characterized by the absence of a hull. Rafts are usually kept afloat by using any combination of buoyant materials such as wood, sealed barrels, or inflated air chambers (such as pontoons), and are typically not propelled by an engine. Rafts are an ancient mode of transport, and naturally-occurring rafts such as entwined vegetation and pieces of wood have been used to traverse water since the dawn of humanity. Human-made rafts were traditionally constructed of wood, bamboo, or reeds. Modern rafts may also use pontoons, drums, or extruded polystyrene blocks. Inflatable rafts up to the 20th century used flotation chambers made of goat- or buffalo-skins, but since then have mostly used durable, multi-layered rubberized fabrics. Depending on its use and size, it may have a superstructure, masts, or rudders. Rafts can also refer to an aggregation of animals resting on the water, such as a raft of ducks. In addition, "raft" can be used as a verb to mean transporting something by means of a raft, or to travel along or across a river or other body of water on a raft.