The present invention relates to a buoy (B) for mooring devices (D) for harnessing renewable ocean energies which allows being fixed to the device and to the seabed and has reconfigurable geometries, including free horizontal rotation of the device. This buoy allows optimal orientation of the device in variable current areas. The Buoy consists of two main parts (1,2) : an outer part (1) to which the high-strength electro-optical cables joining the buoy (B) with the device (D) are hooked, and an inner core (2) which is joined to the mooring system (18, 22) and from which the energy export cable (16) comes out, the rotation of one part with respect to the other being allowed. The assembly has a series of connection openings in the lower part and an inner airlock which allows using conventional internal equipment.