Abstract: In a longitudinally split bottom dump barge which is opened and closed by rotation of the two longitudinal halves of the barge relative to each other about a longitudinal axis on the top side of the barge by hydraulic pistons, a mechanical device for locking the two halves of the barge together in their closed position includes a hook member, rotatably mounted on a shaft at the bottom inner side of one first barge half. When the hook is in its lowered locking position, it hooks about and rests upon a locking pin mounted at the bottom inner side of the other second barge half. An operating shaft linkage has one end pivotably attached to the hook and a threaded opposite end which engages with a hand wheel located on the top deck of the first barge half. The hand wheel is manually turned in one direction to raise the end of the hook member engaging the lock pin, to thus allow the split bottom of the barge to be opened.