As it expends less energy than traditional strokes, it is often used by swimmers to rest in between periods of exertion without having to leave the water.
In figurative language, the expression "treading water" has become a metaphor for an effort expected to create motion, but which actually results in merely staying in one, possibly barely sustainable, place.
Any sort of movement that allows the swimmer to do this can be classified as treading water, but it is more efficient to move the arms and legs in a specific fashion.
Non-swimmers often splash and kick in an effort to stay above the surface but their lack of technique along with shortness of breath and the panic factor make for a very ineffective method of treading water.
[3] Furthermore, the eggbeater kick is also used in synchronized swimming since it grants stability and height above the water while leaving the hands free to perform strokes.
Using the eggbeater, swimmers can also perform "boosts", where they use their legs to momentarily propel themselves out of the water to their hips or higher.