A hovercraft has fans the blowdown through the hull of the ship and a rubber skirt around the edge of the hull to hold the air in so the hull stays above the water. This reduces drag. It also means that a hovercraft can operate on land if the skirts are tough enough to handle it. Hovercrafts can drive right up onto a beach. But because the air escaping from under the skirt causes a lot of splash and spray, hovercrafts are not very commercially useful. Small ones are fun toys, and large ones are good for getting military troops to shore quickly.
A hydrofoil has usually 2 or more fairly narrow âwingsâ that protrude on struts below the hull, and while the ship is moving the motion of the wings through the water lifts the main hull out of the water. This not only reduces drag, but the ship can maintain a steady ride even as the main hull passes over waves. Some fairly large and comfortable ocean-going ferries are hydrofoils.
A hydroplane has a gently curved, almost flat hull that skims on the surface of the water. Many even have a tunnel shape to catch the air, and at high speeds, it traps air under it to help the hull ride up even higher. They require smooth water and can be unstable. Some racing boats are hydroplanes.
