Abstract: A design for the bottom of a boat is provided which has particular applicability for the case of single-screw planing boats. The invention comprises stepped regions in each after outboard corner of the hull bottom which are sized and configured so as to give a substantial reduction in wetted bottom area, while at the same time avoiding encroaching on those two regions of the hull bottom which it is desirable to have remain in contact with the water surface in the planing condition. The first of these bottom regions which it is important to have remain wetted is a narrow arrowhead-shaped band which begins at the forward boundary of the region of the bottom which is wetted by solid water at high speed and extends for a short distance aft. This is the region of high pressure on the bottom of the boat which supports its weight in the planing condition.