I remember working with my swim coach. After a warm up, he said, "Ok Jason, let's get started."
The first drill lead to the second, 10 minutes turned into 20. I was feeling good, comfortable, at ease even... then, Rick said something that jarred me to reality.
"Ok, this time, close your hands into fists and swim down to the end of the pool."
So, I pulled my hand together and wrapped my thumbs around my fingers curled in the palm of my hand...and I swam.
And I swam, and I swam. Where I average 21-23 seconds per lap swimming 25 meters, I reached for the wall and saw the clock was at 39 seconds; it was as if I had regressed to "pre-swimming lessons" times!
We worked through a few more drills. I learned even more about body position, head position, arm entry and more. Most of all, though, that lesson has stuck with me because of how slow I was going - only to realize that I was not just swimming slowly, I was swimming powerfully. Deliberate and focused, the "forearm pull" of the stroke was all I had to move through the water.
As a result of that drill, I believe I'm a stronger, faster swimmer, and I'm much more conscious of how I'm using my body.