There are two events, the duet and the team (of eight), both for women only, in a pool that must be 20m by 30m that contains a square 12m by 12m where the water is at least 3m deep. The water must be between 25 and 27 degrees centigrade and clear enough for the bottom of the pool to be visible. The duets perform technical and free routines in a preliminary round. The top 12 duets advance to the final, in which only the free routine is swum again.

There is no preliminary phase In the team event. The eight teams who qualify for the Games compete in a straight final, in which they perform technical and free routines.

Routines are performed to music chosen by the competitor and within a time limit. Technical routines must be completed with 10 seconds of 2 minutes 20 seconds by duets and 2 minutes 50 seconds by teams. Free routines last four minutes for duets and 5 minutes for teams. In the free routine there are no restrictions on music or choreography, though the technical routine must include boosts, rockets, thrusts and twirls.

There are two panels of five judges, one watching for technical merit, the other for artistic impression. Marks are awarded out of 10 for execution, synchronisation, degree of difficulty and artistic impression.

While the technical routine requires swimmers to perform a fixed set of elements, the free routine must show creativity and flair in pattern work, use the whole of the pool and include contrasts in mood and tempo. Aerial displays, some in which swimmers are thrown from the water by their teammates, count for much.

At the start of routines, fancy footwork on the deck must last no longer than 10 seconds and should indicate the theme of the routine to follow. Underwater speakers belt out music to enable the women to synchronise fully at any stage in their routines.

The scoring, recorded electronically and manually, is complex. Highest and lowest scores within each group of five judges are discarded, and the remaining three are averaged out. The technical merit score is then multiplied by six to give it a 60 per cent weighting, while the artistic-impression score is multiplied by four. The total is the final score for a routine. However, the technical routine score is multiplied by 0.35, and the free-routine score is multiplied by 0.65 to give the free effort a 65 per cent weighting.