cylinders not shown positioned so that when the cylinders are retracted the tunnel sponsons are raised to clear the tunnel openings in the transom in the illustration the twin engine vessel is in the flat bottom hull configuration with the bottoms of the sponsons in the same plane as the bottom edge 120 b of the transom 120 the pneumatic cylinders attached to the middle sponson 30 c the intermediate sponsons 30 h and the end sponsons 30 e are fully retracted as explained hereinabove the pneumatic cylinders attached to the tunnel sponsons are partially retracted so that the bottom 30 b of the tunnel sponson is in the same plane as the transom bottom edge 120 b fig8 shows the twin engine vessel 100 t transformed to a v hull configuration the middle sponson 30 c extends below the bottom edge 102 b of the transom the end sponsons 30 e extend slightly below the transom bottom edge 120 b the intermediate sponsons 30 h including the tunnel sponsons 30 m u2032 extend in a staggered manner the intermediate sponsons 30 h adjacent to the end sponsons 30 e extend below the transom bottom edge 120 b slightly below the end sponsons the closer the intermediate sponson 30 h and the tunnel sponson 30 m u2032 is to the middle sponson 30 c the greater the intermediate.