PURPOSE: To prevent the movement of a mooring buoy with a large amplitude from being transmitted to a seawater pipe as much as possible when the sea is rough, by fixing mooring cables to a buoy and allowing them to support the weight of a water shoot and a cooling pipe etc.

CONSTITUTION: As the both ends of a frame 18 are pin-swivelled, a buoy 1 rises and lowers smoothly and flexible pipes 10 and 16 follow the buoy. Namely, when the buoy 1 rises and lowers, the movement is transmitted to a pipe supporting body 24, water shoot 22, and a water cooling pipe 26, and these bodies rise and lower integrally. In rising and lowering, the pipe supporting body 24 is guided by a rubber damper 25. The pipe supporting body 24, watershoot 22, and the water cooling pipe 26 are constituted so as to have the weight larger than the appropriate buoyancy, and act as the spring having a small spring constant according to the combination of mooring cables 28 and suspending cables 30. Therefore, only a comparatively small movement is transmitted to the pipe supporting body 24 under the sea surface, even if a large amplitude is developed on the buoy 1.