text: A fast current of water flowing over a rock near the surface of a stream or river can create a rooster tail—such commotions at the waters surface are avoided by boaters due to the near surface obstruction.  Propellers on boats can produce a rooster tail of water in their wake, in the form of a fountain which shoots into the air behind the boat.  The faster a boat goes, the larger the rooster tails become.  The efficiency of a boats hull design can be judged by the magnitude of the rooster tail—larger rooster tails indicate less efficient designs.  If a water skier is in tow, the skis also throw off a rooster tail.  Airplanes lifting off from a lake produce lengthening rooster tails behind their amphibious floats as their speed increases, until the plane lifts off the surface.