I have only a very modest suggestion with this segment:
Originally Posted by terry
This reflects a fundamental fact that any swimming coach or teacher must understand: Humans were not designed, by evolutionary biology, to swim:
I would add "efficiently" here, because most people can still swim naturally (ie without any teaching) in a dog like manner (I had in mind baby swimmers). I don't think it would weaken your following arguments.
I would also favor "propulsion" vs "the essential activity" for clarity (in the paradigm end section). Maybe you could also talk in this section about the dogma on sinking legs being linked to a deficiency in kicking (vs your equlibrium approach and always keeping an arm in the frontal quadrant).