Abstract: A vessel for transporting floatably onloaded and offloaded cargo (typically barges) is disclosed. A hull having a well deck surrounded on three sides by the bow, port and starboard vessel's sides has a plurality of ballast tanks adapted to be filled with sea water. When the ballast tanks are flooded, the hull is in a loading configuration wherein the well deck is submerged so that cargo can be floated over the well deck and positioned thereon. At this submerged position of the well deck, the continuous sidewalls of the vessel are interrupted by a series of horizontally elongate water level ports constituting a large interruption of the water plane of the vessel. These ports are concentrated in the area of the forward well deck bulkhead and impede the formation of standing waves within the vessel whereby destructive motion between the carrier vessel and the floating cargo can be prevented from damaging the carrier vessel, floating cargo, or both.