A pontoon is a buoyant device, either of solid lightweight material or constructed as a watertight chamber, used to support objects above or below water.

Pontoons may be simply constructed from closed cylinders such as pipes or barrels or fabricated as boxes from metal or concrete. These may be used to support a simple platform, creating a raft. A raft supporting a house-like structure is one form of houseboat.

Pontoons may be used to support docks or floating bridges. In the case of a dock the entire device is sometimes called a pontoon.

Pontoons of sophisticated construction and shape are used to support aircraft so that they may be operated from water. Such pontoons may also contain landing gear so that the aircraft may operate on both land and water. Such aircraft are called amphibious floatplanes. Floatplanes are distinct from flying boats in which the aircraft fuselage forms a watertight hull.

Pontoons are useful in the salvage of sunken vessels. They be used to support winches that lift the boat via cables. In other cases they may be sunk and attached to the vessel and the water inside then displaced with compressed air.

Pontoon is also the name of a card game [1].