How water polo works at the Olympics

HOW WATER POLO WORKS AT THE OLYMPICS:

* The pool of play in Rio is up to 20m wide and up to 30m long for the men's event, and up to 20m wide and 25m long for the women's event. It is 2m deep

* Played by teams of seven, matches are divided into four periods of eight minutes

* Starting with a race to the ball at the centre of the pool, each team has 30 seconds to attempt to score before the ball is returned to the opposition

* Players aren't allowed to touch the sides or the bottom of the pool during play

* For the round-robin stage, teams are divided into two groups of six in the men's competition and four in the women's.

* The top four teams from each of the men's groups progress to the quarter-finals, with those winners advancing to the medal rounds.

* From the round-robin stage, the overall top four women's teams proceed to the medal rounds.