in a method and a device for tracking an object , especially a subsea object , while utilizing a mother vessel or an intermediate craft equipped with sonars for the transmission and reflection of searching rays which on a display on the vessel indicate one or more objects in the subsea search area , there is provided a searching unit which is controlled from the vessel , and which comprises at least one transponder / responder or the like , for the transmission of signals corresponding to the searching rays . the signal is registered on the display on the mother vessel and is used for guiding the searching unit towards a selected object along the searching rays of the sonars .