Treading water keeps you upright in the deep water with your head out of the water. This is an important personal safety skill for all swimmers. Swimmers must master treading water before taking a lifeguarding class. You can tread using your arms only your legs only or arms and legs together. Use the scissors kick, frog kick (or breaststroke kick) or rotary kick along with sculling movements of the arms and hands. You should learn to tread water in a relaxed way with slow smooth movements. Move the arms and legs only enough to keep your body vertical.
To tread water, stay nearly vertical with your upper body bent slightly forward at the waist. Make continuous broad, flat, sculling movements with the hands a few inches below the surface in front of the body. Keep the elbows bent. Do the sculling movements with a much wider reach than you use to hold your position when floating on your back. Do the scissors or frog kick with just enough thrust to keep your head above water.
The rotary or ‘egg beater’ kick is also effective for treading water. It gives continuous support because there is no resting phase. This strong kick is used in water polo, synchronized swimming and lifeguarding.
To tread water with the rotary kick, stay in the same position as treading water with other kicks. Your back should be straight. Keep your hips flexed so your thighs are comfortably forward. Flex your knees so your lower legs hang down at an angle of nearly 90 degrees to the thighs. With your knees slightly wider than your hip distance apart, rotate you lower legs at the knees, one leg at a time. The left leg moves clockwise and the right counter-clockwise. Make a large circular movement with the food and lower leg. Reach as far sideways and backwards as you can while keeping your body position. As you move each foot sideways and forward, extend it sharply. The power of the kick comes from the forces created by the sweeping action of the leg and foot. As soon as one leg completes its circle, the other starts. Kick just hard enough to keep your head out of the water.
Taken from American National Red Cross “Swimming and Water Safety”, 2004