A disconnectable mooring assembly for a vessel comprises a mooring buoy and a swivel positioned above the mooring buoy. The mooring buoy is provided with a central member for being anchored to the seabed and comprises a number of passages each adapted for receiving a riser. The mooring buoy further comprises an outer member surrounding the central member and capable of a rotation relative thereto. Said outer member is adapted to be housed in and locked to a corresponding receiving opening of the vessel. The swivel is located above the mooring buoy in such a manner that an interspace is defined between the mooring buoy and the swivel.