Float, or buoyancy, is the ability of an object to remain on the surface of a fluid, such as water. This phenomenon occurs when the upward force exerted by the fluid is equal to or greater than the weight of the object. If an object is less dense than the fluid, it will float; if it is denser, it will sink. The principle of buoyancy was first described by the ancient Greek scientist Archimedes. He stated that an object submerged in a fluid experiences an upward force equal to the weight of the fluid it displaces. This principle helps explain why boats and other vessels can float on water.