Proving superior head position
When I do childrens lessons I keep a 20m section of rope in my swim gadget basket. I tie a small loop in one end. Then I give that loop to a swimmer, have them get out in the pool to the end of the rope. I stand on deck ready to reel the rope in. They will lay flat on the water surface with arms extended in front in long streamline position (I call it "Be LONG like a pencil!").
Then I instruct her to lift her head to look a little forward as I reel her in at a steady pace. Then we do it again, while their head is down, ears tucked between the shoulders as I say, and I have her tell me the difference she felt. Then I switch places and have her reel me in while I place my head in different positions so she can feel the change in force she has to apply to keep me coming at a steady pace as my head position changes.
It becomes instant sensory proof to every single student what the superior hydrodynamic head position is. Any angle adjustment in the head is immediately registered in a force change by the arms/hands of the one reeling in, and in the feel of water pressured against the head of the swimmer.
It is an easy way or a coach or swimmer to validate what physiologists, therapists and those studied in hydrodynamics will tell us. Keep that head looking down and entire spine in line.
I stand my students in a line, walk to each one and touch the crown of the head - that point where the spine would poke out of the skull as if on a shishkabob stick - and tell me swimmers that this is the head of their torpedo. Where that points is where their energy will go. So let's keep it pointed straight down the lane.
By concentrating on pointing that 'laser lead' shishkabob line toward the far wall, it can really helps the head find the best position between the arms during the push-off.