 For competition the pool must be a minimum of 20 metres by 30m and, within that, a 12m by 12m area must be at least 3m deep. The water temperature must be 26 degrees celsius, plus or minus one degree. It is also essential for the water to be clear enough that the bottom of the pool is visible as the swimmers use the lines on the bottom of the pool, as well as other markers, to maintain their bearings at all times. Noseclips
Each swimmer will also wear a protective noseclip which allows them to remain under water for longer periods. Music
An underwater speaker is used so that swimmers can hear their music while under the surface. | 
