Water skiing (also waterskiing or water-skiing) is a surface water sport in which an individual is pulled behind a boat or a cable ski installation over a body of water, skimming the surface on two skis or one ski. The sport requires sufficient area on a smooth stretch of water, one or two skis, a tow boat with tow rope. In addition, the skiers are towed by a boat and the categories are Slalom, Tricks and Wakeboard.