The invention is directed at increasing the degree of freedom in layout of the resonator, and the exhaust system including the resonator will be improved. Also, the invention is directed at a resonator and exhaust system wherein when an attempt is made to raise the engine speed from the idling state, the engine speed will be smoothly raised. According to the invention, there is provided a bilge pump for draining water within a hull; cooling water is caused to flow within an exhaust pipe of an engine; and in the exhaust system, there is provided a resonator. The resonator is connected to the bilge pump through bilge pipes. The bilge pump is constructed of a jet propulsion pump to be driven by the engine. Even if the resonator is arranged below the water line, the water which accumulates within the resonator will be drained by the bilge pump, and it becomes possible to arrange the resonator below the water line without interfering with the function of the resonator.