Deep gutters catch surface wave and don't allow them to wash back into the pool and affect the race. These are made of individual finned disks strung on a cable which rotate on the cable when hit by a wave. The rotating disks reduce waves in a competitive pool. World records may be set in long and short course competition. The Olympic Games, as well as most major swimming competitions, are conducted long course.
Various judges watch the swimmer's strokes, turns and finishes or are timers.
A perfect exchange will simultaneously have the finishing swimmer's hand on the touch pad and the starting swimmer's feet just touching the starting block with the rest of the starting swimmer's body extended over the water. A roll is usually caught by the starter and called a false start, but swimmers will often try to guess the starter's cadence and get a good start. Similar to illegal procedure in football. The removal of the hair provides less resistance between skin and water and heightens a swimmer's sensations in the water. Most high school and collegiate competitions in the U.S. are conducted in short course yards.