Invented in the late nineteenth century in Great Britain and played in many countries around the world, notably including Hungary, the game involves teams of seven players (plus up to five substitutes), with a ball similar in size to a soccer ball but constructed out of waterproof nylon. The goal of the game is to throw the ball into the team's goal net at the end of the pool, and prevent the opposition from doing so at the other end of the pool.
The game is divided into four quarters, each of seven minutes. The clock is not stopped within a quarter. A team may not have possession of the ball for longer than 35 seconds without shooting for the goal - after this time, possession passes to the other team.
Dimensions of the water polo pool are not fixed and can vary between 20 x 10 and 30 x 20 metres, and are filled with water to a minimum depth of at least 1.8 metres. The goals are 3 metres wide. 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.
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 the opposition unless they are holding the ball. This allows considerable amounts of holding and pushing to occur to the ball carrier in addition to the holding pushing - and worse - which take place under water and off the ball.
If a player is caught committing a sufficiently bad foul, typically an act of brutality , they are sent out for 20 seconds or until the next goal, whichever comes first. This creates a 'man-up' situation in which the attacking team can reasonably expect to score, typically by adopting a 4-2 formation, and moving the goalkeeper out of position. If a player is sent out three times, they must sit out the whole match.
At long range from the goals, shots at goal are usually easy for goalkeepers to stop, but from closer in are very difficult. Hence, offensive and defensive tactics often superficially resemble basketball.
Men's water polo was the first Olympic team sport in the 1900 games, but women's water polo was only introduced in the Sydney 2000 Olympic Games after political protests from the Australian women's team. Such protests were rewarded when Australia won the gold medal match against the United States with a "buzzer-beater" last-minute goal.