A humidifier is configured to humidify a flow of pressurized respiratory gas. The humidifier includes a tub base configured to retain a body of water and a tub lid configured to cover the tub base. The humidifier also includes an inlet passage configured to receive the flow of pressurized respiratory gas and deliver the pressurized respiratory gas to an interior of the humidifier. At least a portion of the inlet passage is configured to float on the body of water retained in the tub base.