The invention concerns a group of vessels (24), having an unmanned surface vessel (3) and an unmanned underwater vessel (1, 1a), wherein the underwater vessel comprises a location device, in particular a sonar device, for sensing location data (12) in the underwater area and one evaluation unit or more evaluation units, and the evaluation unit or the evaluation units are arranged in such a manner that these comprise detection means (20) for detecting (14) a contact (MILEC) with the aid of the sensed location data (12) and with classification means (21) for classifying (15) the detected contact (MILEC) as a mine-like contact (MILCO) or non mine-like contact (NONMILCO), whereby classification is accomplished by comparing the contact (MILEC) with known mine information so that a mine-like contact (MILCO) can be identified as a mine contact (MINE) or as another object (NOMBO).