The invention relates to a sand and gravel dredge in which, for discharge ashore, the cargo is re-slurried in the hold by high pressure oscillating water jets at the center of the hold floor, creating a turbulent region from which the re-slurried material enters a duct keel through selectively-operable valves and is pumped to dewatering screens at deck level. The dewatered material from the screens is conveyed ashore and the water passing through the screens is directed into settling tanks from where it is recirculated to the high pressure jets.