Treading water is usually the first thing you learn when you start swimming lessons, and it could be the one thing that saves your life if you are ever stuck in deep water for any length of time. Treading water is a technique used to keep your body afloat and your head above the surface so you can breathe. Conserving energy and staying calm are key factors when treading water.
When you are treading water in any situation, you need to remain as relaxed as possible. Anxiety will cause your muscles to tense up and could cause cramping or hinder your technique. As long as your head is comfortably above water, breathe deeply and evenly and you will be able to maintain your position for much longer.
Sculling is a technique you use with your arms and hands that helps keep the water at your shoulder level. While you are in a vertical water-treading position, you bend your elbows slightly and extend your arms out to the sides at shoulder level. You turn your palms to the front at 45 degrees and bring your arms toward the front at the same time. Turn your palms over so they are 45 degrees toward the back when your arms are half way to the front. Continue in this fashion to keep pressure against the water and keep your body near the surface.
While you are moving your arms in a sculling motion, you must also move your legs. The flutter kick is a useful leg movement for different swimming strokes, and for treading water. Basically, it is just an alternating kick with one leg and then the next, in short movements with your toes pointed toward the bottom of the pool. Vary the speed of your flutter kick as you learn how to tread water, to find the speed that works best for your body type.
The timing and coordination of your upper and lower body is what really keeps your head above water. You can have the nicest flutter kick and the most efficient sculling technique, but if the moves aren't coordinated you're going to sink. Practicing your coordination with a water noodle will give you a margin of error while you learn. Wrap the noodle around your back so the ends are under your armpits. Do the sculling technique and the flutter kick at the same time until you can feel yourself being supported without help from the noodle. Eventually, remove the noodle, but have a lifeguard or strong swimmer close by in case you need help.