A mooring device (100) includes a method for operation. The mooring device (100) has an attachment unit (101) including a contact surface (102) for contacting a surface of an object (201) to be attached and at least one magnet for generating a magnetic field through the contact surface (102) to the object (201), a regulator (104) for adjusting the magnetic field generated by the at least one magnet, a telescopic arm (105) pivotally attached to the attachment unit (101), a first hydraulic cylinder (106) and a second hydraulic cylinder (107) attached to the telescopic arm (105), and a monitor for monitoring linear displacements of the first hydraulic cylinder (106) and the second hydraulic cylinder (107). The regulator (104) is configured, based on the linear displacements, to adjust the magnetic field so that an attachment point on the surface of the object (201) can be changed.