A standard (championship) course is 30m x 20m for men and 25m x 20m for women. The depth should be at least 1.8m. Despite these regulations, many non-standard (smaller) courses are in use throughout the USA.

The field of play is segmented into zones marked by colored markings along the side of the pool:

• Goal line - white
  A goal counts only when the ball goes completely across the goal line and into the goal (close does not count); the ball is out of bounds if it goes completely across the goal line and not into the goal
• 2-meter line - red
  No offensive player is allowed to swim inside of the 2-meter line unless he/she has possession of the ball
• 6-meter line - yellow
  If a defensive player commits a foul inside of the 6-meter line, which prevents a "probable goal," the defensive player is charged with a penalty (personal) foul and the opposing team is awarded a penalty throw (a "6-meter"). If an offensive player is fouled outside of the 5-meter line, the offensive player may pick up the ball and take an immediate shot at the opponent's goal (i.e., two players do not have to touch the ball before a goal can be scored)
• Center line - white
  Mid-pool: After each goal is scored, play is re-started at mid-pool; the goalkeepers are not permitted to go across the mid-pool line.

Each team must have seven players (six field players and one goalkeeper) in the water when the game starts. Normally, the home (or higher seeded) team wears white (or light colored) caps, starts the game to the left of the scoring table, and is on the left (or upper) portion of the scoreboard. The visiting (or lower seeded) team wears blue (or dark colored) caps, starts the game to the right of the scoring table, and is on the right (or lower) portion of the scoreboard. The goalkeepers wear red caps with earguards and numbers to match those of their teammates. Either team may substitute players freely after a goal is scored, during a time-out, or between periods. During actual play, substitutions must occur through the team's re-entry area (the corner of the pool in front of the team's bench).

The referees whistle two different kinds of fouls: minor (ordinary) fouls and major (personal) fouls. There is no limit to the number of minor fouls a player may commit. In contrast, once a player has committed three major fouls, that player must leave the game and may not return.

The referee normally signals a minor foul with one blast of the whistle and holding one arm out straight in the direction of the attack. If the minor foul is whistled against the team with the ball, the referee normally signals this with two blasts of the whistle but the arm signal is the same. After a minor foul, a member of the fouled team puts the ball into play by taking a free throw. If the foul is committed outside the 5m line, the player may take the free throw as a "direct shot" at the goal.

The most common minor foul is impeding the free movement of a player who is not holding the ball. This is a standard defensive tactic and the majority of the whistles that lead to free throws are for impeding. Other (less common) minor fouls are whistled for:

• Delaying too long before taking a free throw
• To waste time (most often when a team elects not to shoot the ball and instead throws the ball to a vacant part of the pool and swims away without trying to retain possession)
• Holding the ball underwater so that the opponent cannot play it
• Touching the ball with two hands (does not apply to goalkeeper inside of the 5-meter line)
• Walking on or pushing off the bottom of the pool (does not apply to the goalkeeper inside of the 5-meter line)
• Tipping the ball out of the field of play
• Failing to take a shot within 30 seconds (letting the shot clock expire)
• For the goaltender to go past the center line

A major foul is assigned to the player who commits it. Thus, a major foul is often referred to as a personal foul. Some major fouls result in the player being excluded for 20s, some for the entire game with a substitute allowed back in after 20s, some for the entire game with a substitute allowed back in after four minutes, and some with a penalty throw awarded to the opposing team. The referee normally signals an exclusion in this manner: (1) two short then one long blast of the whistle; (2) pointing at the excluded player then moving the arm towards the re-entry area; then (3) putting up one or both hands and signaling the number of the excluded player. For exclusion with substitution, the referee makes a circular motion with both hands. For a brutality foul, the referee crosses his/her forearms with the hands in a fist. The referee signals a penalty foul in this manner: (1) two or three blasts of the whistle; (2) the number 5 held up with the right arm; then (3) putting up one or both hands and signaling the number of the offending player.

The most common major exclusion foul is holding, sinking, or pulling back a player who is not holding the ball. Other (less common) exclusion fouls are whistled for interference with a free throw or for kicking or striking.

The exclusion with substitution is reserved for serious infractions. Generally, this kind of a foul is assessed either for violence or disrespect. Although there are other situations where this can be the result, they are very rare.

The brutality foul requires that the offending player demonstrate obvious intent to injure another player. This is much more serious than mere violence. As a result of this foul: (1) the offending player is removed from that game and (at least) the next game; (2) that team may not substitute for that player for four minutes of game time; and (3) the offended team is awarded a penalty throw. Brutality occurs very rarely.

A penalty foul is awarded when a player commits any kind of a foul in the penalty area (inside the 5m line) that, in the opinion of the referee, prevented a probable goal. This is most commonly awarded in situations where the attacker turns or gets inside the defenders and is fouled from behind.

When the behavior of participants not in the water (players, Coaches', or any other team personnel) is inappropriate, the referees can issue yellow or red cards. The yellow card is reserved only for the head coach and is a warning that the behavior of someone (including the head coach) on the bench is inappropriate. The red card is awarded when the behavior is bad enough that the referee must order that person to leave the bench. Someone who receives the red card may not have any visual, verbal, or electronic communication with any member of the team for the remainder of that game and all (including the pre-game warm-ups) of the next game.

 Playing Rules - USA Water Polo