To preserve a sea area environment in the circumference of a diving spot and to enhance the convenience and safety of diving users by forming a self-supporting stretch mooring buoy installed in a diving point, of a floating part and a mooring part and by forming the mooring part of a mooring rope and a sinker.

A self-supporting stretch mooring buoy 2 is installed in a diving point P. The buoy 2 is formed of a floating part 4 and a mooring part 5. The mooring part 5 is formed of a mooring rope 8 and a sinker 9. A marker lamp 18 is provided on the top of a support 6 so that the presence of the buoy 2 can be confirmed at night and in dense fog. A boundary display board 21 displaying the radial dimension of the diving area is attached to a handrail part 20 provided around a landing 19 in the upper part of a floating body so as to display the diving area to a vessel navigating in the circumference. A corner rubber 22 is provided in the circumferential edge of the floating body 7, and a fender 23 and mooring metals are providing in the floating body draft part so that vessels such as a leisure boat can be moored.