Hydroplane is a high-speed motorboat that skims over the water almost in the way a flat skipping stone does when thrown. The boat’s bottom is shaped to lift the hull as it speeds up, until the boat is “planing” over the surface. The shape of the bottom allows the pressure of the water to lift the boat and keep it on the surface as long as it keeps moving quickly. For this reason, the bottom must be flat, or only slightly curved. In some hydroplanes, the bottom is a single surface. Others have two or more separated bottom sections. Many racing hydroplanes are called “three-point” boats. The only parts of the boat that touch the water at high speed are a float, or sponson, on each side of the hull, and the propeller. See also Motorboat racing .
