Check out this short video by USA Water Polo for a great explanation and demonstration of the “egg-beater” style of treading water during water polo.
Water polo can be compared to basketball or soccer. Instead of running, however, athletes swim – freestyle and backstroke, up and down the pool. When they’re not swimming, they’re treading water. Players never stand on or even touch the bottom of the pool. Therefore, one of the first things we teach new participants is “egg beater” – the very efficient water polo method of treading water.