Artificial waves are human-made waves usually created on a specially designed surface or in a pool. Making waves Surface waves can be created by any moving object displacing fluid: turbine blades, paddles, a hand, a flung stone, etc. Each pulse of water (or crest) pushed outward from the disturbance leaves a space (or trough) behind it which causes another, smaller pulse to follow: thus a thrown stone's single impact causes a series of ripples. Larger waves can be built up if a series of movements are timed to reinforce waves' motion, much like a person sliding back and forth in a bathtub. Boundaries and obstacles also shape waves by concentrating or dissipating some of the wave's energy. When fluid flows over a surface which diverts it upward, this flow can rise above the rest of the fluid in a standing wave which remains in one place while the flow lasts. An example of a natural standing wave may be found in swift-flowing streams, downstream from a boulder in the stream bed. Artificial reefs can also be placed into natural wave environments to enhance the quality of the incoming breaking wave for surfing. Wave focusing areas can build up wave power and height prior to breaking, and breaking surfaces then trip the wave up to make it break; the surfing surface then carries the breaking wave along an angle that maximises its value for surfing. Applications In a wave pool water is pushed out of an opening with enough force to create a wave-like shape. Riders can ride this type of wave on a regular surfboard. Wave pools go as far back as the 19th Century, as famous fantasy castle builder King Ludwig of Bavaria electrified a lake to create breaking waves. In 1929, a Pathe Pictorial there is film of "Indoor Surfers" frolicking in small, artificially-generated waves in a swimming pool in Munich, Germany. The waves were created by agitators which pushed waves through the diving area and into a shallow area - where kids were bodysurfing little waves: "This is the new kind of swimming bath that is becoming the rage of Germany," one of the captions reads. "No more placid waters for bathers - the mechanism behind the netting keeps everything moving." In 1939, a public swimming pool in Wembley, England was equipped with machines that created wavelets. Not for riding, but to approximate the soothing ebb and