In water polo, the goalkeeper occupies a position as the last line of defense between the opponent's offence and their own team's goal, which is 2.8 m2 (30 sq ft).
The goalkeeper is different from other people on their team; they possess certain privileges and are subject to different restrictions from those of field players. As well as this, they must possess different skills from those of the fielders.
Goalkeepers often have longer playing careers than field players because they swim far less.
In water polo, the goalkeeper is commonly known as the goalie or keeper and may also be known as the man/woman in the cage.
The position of the goalkeeper has existed since the game of water polo originated. At that time, the object of the game was to touch the ball on the opponent's end of the pool. The goalkeeper would wait at the end of the pool until an opposing player approached the goal, when the goalkeeper would try to stop that player, for example, by dunking their head.
A change occurred in the game and the role of the goalkeeper in the 1880s, when the Scottish reduced the size of the scoring area by placing rugby posts, spaced about 10 feet apart, at each end of the pool. At the same time, the rules were changed to allow goalkeepers to stand on the pool deck and leap onto the head of an opposing player who approached the goal. This change in the rules was brief. To prevent the serious injuries that resulted from this method of goalkeeping, the rules were revised again to require the goalie to remain in the water.
The basic functions of the goalie position have changed little over the last century, but there have been changes affecting the style of play. In the 1940s, Hungary introduced a new technique called the eggbeater kick that enables goalkeepers to maintain a stable balance in the water.
Inside the 5 m (16 ft) area, the goalkeeper is the only person on the team permitted to touch the ball with two hands, touch the bottom of the pool and punch the ball with a clenched fist. Although the goalkeeper may not advance beyond the half-way line, they may attempt shots at the other goal.
Any goalkeeper who aggressively fouls an attacker in position to score can be charged with a penalty shot for the other team. The goalkeeper can also be temporarily ejected from the game for twenty seconds if they prevent a likely goal (for example, by splashing). If the goalkeeper pushes the ball under the water in the 5 m (16 ft) area, instead of being a free throw to the other team, it is a penalty. A penalty is also awarded to the other team if the goalkeeper pulls down from the crossbar of the goal to prevent a goal.