If a body moves in a gas, then the frictional drag would be lower than that of the same body moving in a liquid because the frictional drag depends on the dynamic viscosity of a fluid. For example, the viscosity of water is approximately one hundred times larger than that of air. In addition, if there exists a fore-aft pressure difference which is proportional to the fluid density, the pressure drag or the form drag on a body in a gas also would be lower than that of the same body moving in a liquid. For example, the density of water is approximately one thousand times larger than that of air. Therefore, during its motion, if a body is completely enveloped in a single large gaseous cavity, the associated total drag is expected to be significantly reduced. This phenomenon is known as supercavitation. We study on the ventilated supercavity formation in a free-surface bounded environment.