ratio of length of waterline to beam has much importance in marine mechanics and design. Row boats or dinghies are oar powered, and generally restricted to protected waters. Rowboats are generally heavy craft compared to other has Sailing can be either competitive, as in collegiate dinghy racing, or purely recreational as when sailing on a lake with family or friends. Small sailboats also called dinghies are commonly made from fiberglass, and will have wood, aluminum, or carbon-fiber spars, and generally a sloop rig (two sails: a mainsail and a jib, commonly include 3rd sail the spinnaker for going downwind). Racing dinghies and skiffs tend to be lighter, have more sail area, and may use a trapeze to allow one or both crewmembers to suspend themselves over the water for additional stability. Larger trailerable sailboats include trailer sailers, which have enclosed accommodation, and sportboats which are optimised for speed. Daysailers tend to be wider across the beam and have greater accommodation space at the expense of speed. Cruising sailboats have more width, but performance climbs as they tend to be much longer with a starting over-all length of at least re-balancing the dynamic ratio between length of waterline (aiding speed) and beam width (adding cargo and people space). Freshwater fishing boats account for approximately 1/3 of all registered boats in the U.S., and most all other types of boats end up being used as fishing boats on occasion. The boating industry has developed freshwater fishing boat designs that are species-specific to allow anglers the greatest advantage when fishing for walleye, salmon, trout, bass, etcetera, as well as generic fishing craft. Watersport Boats or skiboats are high-powered Go-Fast boats (specialized towboats in fact) is designed for activities where a participant is towed behind the boat such as waterskiing and parasailing. Variations on the ubiquitous waterski include wakeboards, water-skiing, kneeboarding, inflatable towables, and wake surfing. To some degree, the nature of these boating activities influences boat design. Waterski boats are intended to hold a precise course at an accurate speed with a flat wake for slalom skiing runs. Wakeboard boats run at slower speeds, and have various methods including ballast and negative lift foils to force the stern in the water, thereby creating a large and "jumpable" wake. Saltwater fishing boats vary widely in length and are once again specialized for various species of fish. Flats boats, for example, are used in protected,