Abstract: A dredging apparatus for extracting sand, gravel and the like from the bed of a body of water features an improved drive mechanism having an enclosed drive shaft between an above-water carrier to an under-water excavator or the like, the enclosed drive being substantially water-tight and pressurized to at least partly balance the interior of the enclosure means and the bearing and seal contained therein against the under-water pressure exerted externally of the enclosure. More specifically, the enclosure is supplied with fluid from a power source that includes a hydraulic drive means.