The game is divided into four periods, of which the length depends on the level of play:
Olympics: 7 minutes
High School:
Varsity:
7 minutes
Junior Varsity:
6 minutes
Fresh/Soph:
5 minutes
The game clock is stopped when the ball is not in play e.g. between a foul being committed and the free throw being taken and between a goal being scored and the re-start. This causes the average quarter to last around 12 minutes real time. A team may not have possession of the ball for longer than 35 seconds without shooting for the goal or an opponent being ejected - after this time, possession passes to the other team. However if a team shoots the ball within the alloted 35 seconds, and regains control of the ball, the shot clock is reset to 35 seconds.
Dimensions of the water polo pool are not fixed and can vary between 20 x 10 and 30 x 20 meters, and are filled with water to a minimum depth of at least 1.8 meters (at least 6 feet). The goals are 3 meters wide and 1 meter high. The ball used is a water polo ball. One player on each team is designated the goalkeeper, and their primary job is to guard the goals, deflecting or catching any shots at goal. The goalkeeper is the only player who can touch the ball with both hands at any time, and, in a half-deep, half-shallow or all-shallow pool, the only player allowed to stand on the bottom.
Players can move the ball by throwing it to a teammate or swimming whilst pushing the ball in front of them. Players are not permitted to push the ball underwater when being tackled, or push or hold an opposition player unless that player is holding the ball. Water polo players tend to need remarkable stamina due to the considerable amount of holding and pushing that occurs during the game, both that which is unseen/ignored by the referees (usually underwater) and that which is allowed. Water polo is one of the most physically demanding of all sports.
A classic 4-2 man-up situation. The attacking white team has 4 players positioned on 2 metres, and 2 players positioned on 4 metres. The 5 outfield defending blue players try to block shots and prevent a goal being scored for the 20 seconds of man-down play. In the top left corner, the shot clock can be seen, showing 28 seconds remaining in the white attack.
As in ice hockey, players can be sent out for short periods of time for committing fouls. In waterpolo, a player caught committing a exclusion foul, is sent out for 20 seconds, until the next goal, or until his team re-gains possession, whichever comes first. This type of foul is normally called an ejection. If the foul is a non-sportsman like act, however, the player is ejected for the remainder of the game with substitution. This type of foul is often called a roll because the referee signals the foul by "rolling" his hands around one another.
If a player commits a foul with intention to harm, the player is ejected from the game without substitution. The players team plays one man down for the rest of the game. This type of foul is called a brutality and is signaled by the referee by crossing the arms in the form of an X. During a man-up situation resulting from an "ejection", the attacking team can expect to score, by adopting a 4-2 or 3-3 formation, and moving the goalkeeper out of position. A player that has been excluded three times must sit out the whole match with substitution, much like the five personal fouls in Basketball.
At long range from the goals, shots at goal are usually easy for goalkeepers to stop, but from closer in are very difficult.
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