A transferring sea buoy is moored to the sea floor via an anchoring line. The anchoring line comprises a chain and an anchoring device for fastening the chain and the buoy. The anchoring device comprises a deformable longitudinal element having a first end connected to the transferring sea buoy and a second end connected to the chain. The deformable longitudinal element is deformable when the transferring sea buoy moves. The member has at least first and second portion of thin rectangular cross-section, each deformable in one plane to absorb relative motion between the buoy and the chain.