A water polo ball.
A fast-paced, end-to-end sport, water polo guarantees plenty of drama and is thrilling viewing for spectators.
Initially developed as an aquatic form of rugby that was played informally in lakes and rivers, the modern version of the game has become a regular feature of the Olympic programme since first being staged as a medal event at the Paris 1900 Games.
Played in a swimming pool, the sport sees two teams of six outfield players and a goalkeeper battle it out in a roped-off pitch as they attempt to score the most goals using a volleyball-sized ball.
The deep pool means that players must tread water throughout a game, demanding extreme athleticism and stamina across the course of a 32-minute match.
Games are played over four periods of eight minutes in an area measuring 30 metres long and 20m wide, with the goal being 3m wide and 90 centimetres high and floating on top of the water.
As well as the strength needed to stay afloat while being able to catch the ball as well as passing and shooting one-handed, players must also grapple for possession while swimming and can cover thousands of metres during a game.
Water polo is a dynamic sport where the action is always played at a high tempo, especially as substitutions can be made without the game having to be stopped.
During a match, teams can lose a player if they commit a major foul, giving the opposition a 'man-up' situation to try and take advantage with a 20-second 'power play'.
At London 2012, eight women's teams are split into two groups, with the top two from each group progressing to the semi-finals to battle it out for the medals.
Two pools of six compete for eight quarter-final places in the men's tournament.