Gliding is one of those skills that you must learn well before you execute a good front crawl. Some beginners have a fear of gliding away from the wall. Still others, despite being more advanced, sink parts of their body, making it very difficult to glide.
One of the exercises that I ask my swimmers to do first is to glide towards the wall. By standing about three feet away from the wall, sink down to your neck, and put your hands out in front of you. Grab a big breath of air, bend forward and glide towards the wall. The head should be half in the water before your feet leave the bottom, and the head should remain in the water until the hands touch the wall. Look at the bottom of the pool as you do this drill. If the head is looking forward, your feet will not want to come up. Open your eyes when you swim, so that you know where you are going. The water level should be at the hairline. The back should be either breaking the surface, or be just at the surface. The buttocks should be just below the surface. Make adjustments to the body's alignment by changing the position of the head, and the small of the back. The hands should be about four inches under the water. Relax as much as possible.
On many occassions I've even seen good swimmers body position in the water causing undue resistance to their glide. By doing this drill with corrections as many times as the coach thinks is necessary, swimmers notice their improvement as their efficiency in the water increases with less energy.
~Coach Linda Delzeitt and Coach Pedro H. Ordenes, www.watersworlswim.com