Striving for Mediocrity
Thanks for all of the great ideas folks!
In answer to the questions, my stroke rate is high at 22 per 25 meters. I have gotten it down as low as 18 at times, by exagerating the glide portion of the stroke and hesitating in that position. In an effort to relax and save energy, my torso, elbows ankles and shoulders may be a bit schlumpy since it seems to take a lot of energy to straighten my entire body - I can feel the muscles burning.
Many comments were about breathing. I definitely do not exhale fully because I feel myself sinking when I do that. When breathing heavily, I'm afraid to miss a breath. When I first started trying to learn to swim efficiently, I would breathe only on the right every 2nd stroke, but recently a coach told me to breathe every third, forcing me to breathe on both sides, since my stroke was lopsided. I find that after 100 yards or so, that I'm not getting enough air breathing every third, so now I switch back and forth from left to right, breathing every second stroke, occasionally going every third.
From all this I conclude that I'm grossly inefficient, which leads to my frustration. The Law of Diminishing Returns would predict that fixing a few major flaws would lead to fairly big improvement at first, at least enough to make me a mid-pack swimmer.