Synchronised swimmers will perform two routines, the technical, during which a set number of moves are performed in sequence, and the free, in which the swimmers can devise a routine with their choreographer.
The swimmers will attempt to perform their routines as in perfect time, as flawlessly possible while attempting to make the whole thing appear effortless.
The length of the routine varies depending on the number of swimmers and two sets of judges each assess each routine, one set judging technical merit and the other artistic impression.
Technical merit covers three specific areas: execution, synchronisation and difficulty. Execution covers strokes and other propulsion techniques and the precision of patterns. Movements should be smooth and effortless and swimmers should be high in the water.
Just as in figure skating or gymnastic routines, judges look at the overall "feel" of a routine and mark accordingly. Choreography, body patterns and effect of the music in relation to the routine are all taken into consideration.
When the judges have recorded their scores, the highest and lowest on each panel are discarded and the other three are averaged out to give a final mark.
Scores can be affected by penalties that may be awarded by the judges. Serious point-deductions are possible for rule breaking; for example, a two-point penalty is applied if a swimmer deliberately touches the bottom of the pool.
Two points can also be knocked off if a routine is missing an element. Half a point can be deducted if a part of an element is missing.
Lesser offences like mistakes in timing on a routine result in a one-point penalty. If a swimmer voluntarily stops swimming during a routine, the team or duet will be disqualified.
If, after all the totting up is complete, two teams cannot be separated by their scores up to three decimal places, a tie is declared.