Why do some people have so much trouble learning how to swim?
Technique. It's all about technique - Balance, Symmetry, Rhythm, and Quiet – BSRQ
Balance – is placing your body level with the surface of the water. The more level body mass at or above the water line, the more efficiently your body will pass through the water. Body positioning is controlled by your head, shoulders, and chest. Your body has two center lines when you're standing, one vertical line dividing your body exactly in half, the "symmetry line" and a horizontal line where exactly fifty percent of your body weight resides above and below that "balance line". When your body is horizontal on the surface of the water think of the balance line as a fulcrum. Your goal is to balance your body on that fulcrum so you place as much body mass at or above the water line as you can, without effort. It takes practice, but it'll come. At first you may need a helping hand or forearm to serve as the fulcrum until you can achieve balance on your own.
Symmetry - Externally your body is symmetrical and there's a vertical center line dividing you in half, the symmetry line. In the water you want to rotate your body on that center line, that axis. Bi-lateral breathing is how you accomplish symmetry. Breathing to the right, then breathing to the left, back and forth, breathing on every third stroke. Bi-lateral breathing alone will resolve eighty to ninety percent of a swimmer's stroke deficiencies.
Rhythm - Here's a short You Tube video of an elite speed skater training on roller blades, http://www.youtube.com/watch?v=T.... Watch the rhythm while visualizing your body horizontal on the surface of the water and rotating your stroke and kick back and forth on your center line – stretch, stroke kick, glide... stretch, stroke kick, glide. The kick should be a short push with your extended straight leg to help maintain balance. Over-kicking while bending your knee will disrupt your balance and diminish your efficiency. The video below is an excellent example of how to use your legs, or kick, when swimming efficiently.
Quiet - In water, noise is turbulence, quiet is efficiency. Listen when you swim, the noise you make, your goal is to eliminate it. Become quiet, stealth-like. Slide and glide through the water.
Here's another You Tube video, http://www.youtube.com/watch?v=r.... Excellent example of the Terry Laughlin Total Immersion swim technique. There are many good Total Immersion You Tube videos, most are longer but well worth the time when you have the time.
One thing to remember, the fastest swimmers take the fewest strokes per pool length. It's all about technique, B S R Q and practice.
Kicking – Fins will help strengthen your legs and lower back and create greater flexibility in your legs, ankles, and feet. Your goal is to "kick" with your leg straight when performing the free style or back stroke. If you use a kickboard, which is not recommended, extend the board as far from your body as possible keeping your head as low as possible. This avoids arching your back and stressing your lower back.
Have fun and keep swimming.