Before the eggbeater kick, goalkeepers would use breaststroke which meant that they could not stay up for very long and players found it easier to score.
It is important for the goalkeeper to swim both breastroke and freestyle - the breastroke helping with the eggbeater kick and the freestyle helping with the swimming in the match.
You need the lung capacity to swim two kilometres miles over the course of a game and the stamina to do eggbeater kicks, the hands-free form of treading water.
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.