Abstract: The present invention relates to a device, for dewatering dredged material with a dry substance rate below 15%, comprising a tank (2) which is arranged with at least one inlet (5) for dredged material, a first outlet (8) for cleaned water and a second outlet (9) for sludge; the tank further comprises a mixing chamber (3), to which the inlet (5) for dredged masses leads, and a sedimentation chamber (4) in which the first (8) and the second outlet (9) are arranged. The mixing chamber (3) and the sedimentation chamber (4) are in fluid communication.