Extracts from USA Swimming regulations
103.16 /M/ FLOATING LANE DIVIDERS AND MARKINGS
1 Floating lane dividers shall extend the full length of the course and shall be attached at each end wall with recessed anchors so located that the center line of the cable securing the dividers shall be on the surface of the water with the bottom half uniformly submerged for its entire length. They shall: A Separate the racing lanes. B /LSC/ Be outside the outermost lanes being used.
2 Dividers shall consist of contiguous floats having a minimum diameter of 5 centimeters (2 inches) to a maximum diameter of 15 centimeters (6 inches). The color of the floats extending from the walls the distance of 5 meters for long course and short course meters and 15 feet for short course yards shall be distinct from the rest of the floats.
Distinctive colored floats, or markers extending around the full circumference of the floats, shall be placed at 15-meters (49 feet 2-1/2 inches) from each end wall in both short course and long course pools. A fixed mark shall be placed on any wall or the deck adjacent to an outside lane to correctly align the 15-meter buoys for judging underwater starts/turn distances.
3 /LSC/ A single line of dividers between racing lanes shall be used in long course and short course meters competition. Multiple lines may be installed for short course yards competition, provided the width of water between dividers is not reduced to less than 7 feet.
4 /NC/ Minimum 11 centimeter diameter floats shall be required for National Championships.