Abstract: A water-tight hopper assembly for a self-unloading marine vessel of the type that transports bulk cargo includes a hopper chute formed from a plurality of interconnected wall members converging toward one another in the downward vertical direction, a discharge opening connected to the lower end of the hopper chute, a cargo discharge gate mounted at the lower end of the discharge opening, and a water-control gate mounted within the discharge opening. The water-control gate includes a fixed sealing flange depending inwardly from the plate members forming the discharge opening and a seal member pivotally connected to the sealing flange. The seal member is movable between a closed position and an open position, the seal member cooperating with the sealing flange to prevent passage of water through the discharge opening while in its closed position. The seal member is locked in its closed position by latching dogs pivotally mounted on the exterior of the discharge opening.