Have your child turn onto her back in the swimming pool.
Ask her to hold out her arms on top of the water, like an airplane.
Hold the child's head firmly in both of your hands, covering her ears.
Pull the child gently through the water on her back, so that feet rise to the surface and body remains horizontal, floating on the surface.
Make this like a ride at first, with the emphasis on getting the child comfortable in this position. Comfort and relaxation are the key elements. (See "How to Float on Your Back.")
Demonstrate how to float on your back, taking a deep breath, putting your head back in the water and spreading your arms out to the sides. Kick your feet lightly so that they rise to the surface.
Help your child into the back float position by supporting her head and lower back from underneath.
Feel the child relax in the water. When the child is totally relaxed, slowly lower your hands away from her back so she can float unaided. Keep your hands close by, to support her in case she panics.
Have the child hang onto the wall, put her head back into the water, and push off from the wall into the back float position. Demonstrate and assist this activity.