Abstract: Dredging apparatus comprises a modular, submersible, vertically positionable crater sink mechanism operable to form a crater in a bed of material beneath a body of water. The crater sink mechanism comprises an elongated tubular housing closed at its upper end and having a dredged material intake opening at its lower end. An auger mounted in the material intake opening is rotatable by a reversible hydraulic drive motor and is axially positionable by a linear hydraulic motor. The inner end of the auger cooperates with the closed end of the tubular housing to define a mixing chamber. A clear water inlet port and a mixture outlet port on opposite sides of the tubular housing each communicate with the mixing chamber. The auger is rotatable in one direction to dig into and ingest material (fluidized by ambient water) through the material intake opening and transport it into the mixing chamber.