Sailboats are propelled by the force of the wind on sails, requiring skill and experience to maneuver the vessel in constantly changing sea and wind conditions. Types of sailing include racing, cruising and dinghy sailing, in competition or for recreation. Competition varies from single person dinghy races, to large boats manned by a crew of sailors in multi-million dollar racing campaigns in fleet racing, match racing and distance racing formats. At the high end level, sailing is one of the most expensive sports in the world.