A system has a source of gas venting gas at a nose portion of the vehicle to create a gas/vapor cavity on the nose portion and an adjacent hull of the vehicle. A thermal engine propelling the vehicle through ambient water creates waste heat for heating the hull to raise the temperature of the gas/vapor cavity extending over it. A pump aft on the vehicle recirculates a portion of the gas/vapor cavity as recirculated gas to the nose portion. The velocity of the recirculated gas of the gas/vapor cavity is controlled by the pump to be virtually the same as the relative flow rate of the ambient water along an interface boundary between the gas/vapor cavity and the ambient water.