Abstract: A hull for a boat having a forward section with two twin subhulls or sponsons joined by a bridging structure which forms, approximately midway along the sponsons, the fore-end of a third subhull. The twin forward subhulls each have a modified W cross-sectional shape which is continued to a spoiler located near the mid-section of the hull. Water flowing past the undersides of the sponsons gives rise to a lifting action as the boat starts to move. The bottom of the central subhull runs downward and rearward between the sponsons but remains separated from them past the spoilers. In the rear section, the extension of the central subhull is deeper than the remainder of the hull and has a substantially flat bottom joined to sides inclined outwardly and upwardly to form a generally V cross-sectional shape. As the boat picks up speed, it merely rises in the water with little change of attitude until the aft part of the hull skims on the surface of the water.