A surfboard is an elongated platform used in the sport of surfing. Surfboards are relatively light, but are strong enough to support an individual standing on them while riding a breaking wave. They were invented in Hawaii, where they were known as papa he‘e nalu in the Hawaiian language; they were usually made of wood from local trees, such as koa, and were often over 15 feet (5 m) in length and extremely heavy. Major advances over the years include the addition of one or more fins on the bottom rear of the board to improve directional stability, and numerous improvements in materials and shape.