Olympic Games, however, the duet competition was restored and is now featured alongside the team competition. World Aquatics Championships Synchronized swimming has been part of the World Aquatics Championships since the beginning. From 1973 through 2001, the World Aquatics Championships featured solo, duet and team competitions. In 2003, a free routine combination, comprising elements of solo, duet and team, was added. In 2005, it was renamed free combination. In 2007, solo, duet and team events were split between technical and free routines. Since 2007, seven World championship titles are at stake. In 2015, the mixed duet (technical and free) were added to the competition program. European Aquatics Championships Artistic swimming is part of the program of the European Aquatics Championships from 1974. Basic skills Sculls Sculls (hand movements used to propel the body) are some of the most essential part to synchronised swimming. Commonly used sculls include support scull, stationary scull, propeller scull, alligator scull, torpedo scull, split scull, barrel scull, spinning scull, totem scull, canoe scull and paddle scull. The support scull is used most often to support the body while a swimmer is performing upside down. The support scull or "American Scull" was invented by Marion Kane Elston and propelled the sport to new heights. The sport was transformed from water ballet to the athleticism of modern-day synchronized swimming. See the International Swimming Hall of Fame as a reference. Support scull is performed by holding the upper arms against the sides of the body and the fore arms at 90-degree angles to the body, with hands facing the bottom of the pool. The fore arms are then moved back and forth while maintaining the right angle. The resulting pressure against the hands allows the swimmer to hold their legs above water while upside down. Eggbeater The "eggbeater kick" is another important skill of synchronised swimming. It is a form of treading water that allows for stability and height above the water while leaving the hands free to perform arm motions. An average eggbeater height is usually around collarbone level. Eggbeater is used in all "arm" sections, a piece of choreography in which the swimmer is upright, often with one or both arms in the air. Another variation is a body boost, which is executed through an eggbeater buildup and a strong whip kick, propelling the swimmer out of the water vertically. A body boost can raise a swimmer