Treading water or water treading is what a swimmer can do while in a vertical position to keep their head above the surface of the water, while not providing sufficient directional thrust to overcome inertia and propel the swimmer in any specific direction. 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. They will usually tire quickly and not be able to stay above the surface very long.

Experienced swimmers use a variety of techniques to stay above the surface. These techniques often involve sculling, flutter kick, and other unofficial techniques of staying above the surface.

The eggbeater kick is an efficient method of treading water. It involves the swimmer in a "sitting position" in the water. The swimmer's back must be straight, knees bent so that the thighs are parallel to the surface of the water, and lower legs perpendicular to the surface.

The left foot makes a clockwise motion while the right leg makes a counterclockwise motion towards the axis of the body, in a similar manner to operating the pedals on a bicycle. The legs should never meet as when one foot is on the inside of the motion, the other should be on the outside. The arms are not involved directly in this kick.

The most critical aspect to having an effective eggbeater kick is flexibility. A very good hip motion range is needed to achieve a good eggbeater kick.