The eggbeater kick is another important skill of synchronized swimming. It is a form of treading water that allows for stability and height above the water while leaving the hands free to perform strokes. An average eggbeater height is usually around chest level. Eggbeater is used in all arm sections, a piece of coreography in which the swimmer is upright, often with one or both arms in the air. Another variation is a boost, which is executed through an eggbeater buildup and a strong whip kick, propelling the swimmer out of the water vertically. Eggbeating for a considerable period is also referred to as an aquabob and is used to build propulsion under water prior to a boost or pop up.