The playing area for water polo is 30 x 20 meters, with a minimum of 2 meters of depth. While these are the official dimensions, many high school and club teams will find themselves playing in a much smaller space, due to a shortage of pools that are capable of providing such a large field of play.

At any point in the game, each team is allowed a total of seven players, six field players and one goalie. The home team is designated by dark caps, while the visiting team wears white. All players must tread water the entire game, and are not permitted to touch the bottom or sides of the pool. With the exception of the goalies, all players may only touch the ball with one hand.

Each game consists of four periods. Official period length is eight minutes, although at tournaments and during younger levels of play the length of each period is often shortened to five or six minutes. Each time the whistle blows the play clock is stopped, though play will continue on after the whistle. As a result, games will last longer than the total minutes of official play, generally taking from 35 minutes to an hour, depending on the number of whistles. The time between a whistle and the restarting of the play clock is commonly referred to as “dead time”.

Upon the start of every possession, the offensive team is allowed 30 seconds to take a shot before the ball is turned over. The ball does not need to reach the goal or the goalie to be considered a shot, but must be obviously intended to do so.

During the flow of the game, a team must be in possession of the ball to call a timeout. The number of timeouts per game that are permitted to each team vary according to league and tournament rules, but generally ranges from one to three.

Substitutions can be made after a goal is scored, between periods, during a timeout, for an ejected player in the proper area, or during running time. To make a substitution during running time, the player exiting the field of play must swim to the re-entry area of his or her team and remove themselves completely from the field. Only when that player has successfully reached the re-entry area may another player enter the field of play, provided that he or she enters from that same re-entry area.

Water polo is a game that must have a definite winner. In the event of a tied score after the four periods of regulation, two three-minute periods are played. If after those two shorter periods the score remains tied, a three-minute sudden death period is played. Once in the sudden death portion of the overtime, the first team to score wins the game.

The goal for each team is one by three meters in size. A goal is scored when the ball completely passes the face of either goal line.

Physical contact is very common as players maneuver for position. A foul is indicated when the referee blows the whistle, using hand signals to point out the direction of the foul and where the ball is to be put in play.
 

 Common ordinary fouls include: impeding an opponent who does not have control of the ball; pushing, pulling, or pushing off of an opponent; touching the ball with both hands; putting the ball underwater within the immediate vicinity of an opponent; on offense, entering within the 2M line in front of the opponent’s goal without the ball; and stalling. 

 The number of ordinary fouls a player commits is not recorded, as there is no limit to the number of ordinary fouls a player may commit.

Common exclusion fouls include: holding, sinking, or pulling back an opponent who is not holding the ball; committing an ordinary foul during “dead time”; kicking or striking an opponent; interfering with a free throw; and deliberate splashing in the face.

Exclusion fouls result in a player being excluded for 20 seconds.  Once the foul is called, the excluded player must immediately move to the re-entry area in front of his/her team bench.  The excluded player or substitute for the excluded player may not return until the 20 second exclusion time expires, a goal is scored, or a change of possession takes place, whichever occurs first.

The number of exclusion fouls a player commits is recorded by the game secretary.  Once a player has committed three exclusion fouls, he or she is not permitted to continue play.

One special class of exclusion fouls exists: major fouls.  Players who are assessed major fouls are immediately removed from the game and may not return.  A substitution for that player is allowed in the same manner of a regular exclusion fouls.

Major fouls include: misconduct or disrespect to the referee; foul language; and violent play.

Any deliberate kicking or striking with intent to injure, brutality, constitutes a major foul in which the offending player is removed from the game with no substitution allowed.

Penalty fouls are called when a defender fouls his/her opponent in order to prevent a probable goal from taking place.  Such fouls can only be called when the ball is between the goal posts and within the five-meter area in front of the goal. 

When a penalty foul is called, a penalty throw is awarded to the offended team.  The penalty throw can be taken by any member of the offended team that was in the game at the time of the foul, with the exception of the goalie.  The penalty throw is taken from the 5-meter line, and may be defended only by the opposing goalie.  The goalie must begin the throw with his or her head on the goal line, and the shooter must take the throw in one continuous motion without faking or hesitation.

Penalty fouls occur most commonly when:

	An attacking player is facing the goal, controlling the ball without holding it, and is fouled by being held, sunk, or pulled back.
	Any player strikes or plays the ball with a clenched fist.
	The defending goalie puts the ball under the water.
	Any player pulls or pushes the goal.
	Any player from the sideline enters the water outside of standard substitution time. (This foul does not depend on the location of the ball.)

Penalty fouls are recorded in the same manner as exclusion fouls.  Any player committing any combination of three exclusion or penalty fouls may not return to the game.