Vortex: It goes down. Before the drop the barge displaced both its own weight and the weight of the beam. After the drop it displaces only its own weight. The beam displaces its own VOLUME, but sinks to the bottom, so this volume is much less than the volume of water necessary to float the beam. If the beam floated, then the water level would be unchanged, but the beam is steel, and much heavier.
Vortex: It goes down. Before the drop the barge displaced both its own weight and the weight of the beam. After the drop it displaces only its own weight. The beam displaces its own VOLUME, but sinks to the bottom, so this volume is much less than the volume of water necessary to float the beam. If the beam floated, then the water level would be unchanged, but the beam is steel, and much heavier.