An autonomous dredging underwater device for moving along the bed and suction dredging it, mitigating the environmental impact of its operation which operates in cooperation with a surface support unit, whether floating or on land, which carries out functions such as collecting dredged material, supplying the device electrically and hydraulically, and providing communication means for supervision and/or control which comprises: a) a structural frame (1); b) a drive system (2) with four motorized wheels; c) a dredging unit (3) in which the frame (1) and the drive system (2) constitute a hood around the same to contain the turbidity which is produced during displacement and dredging; d) a concentrator (4); e) a guide system which allows displacement, both remote- controlled by an operator and autonomously according to a predefined route; and f) a flexible tube and associated method.