As was explained in post #7, all the skills are done dramatically differently. Here is a story that you may find interesting.
The article on NB that PADI published a decade ago was originally several times the length of the published version, and Karl Shreeves of PADI was assigned to work with me on cutting it down to size. Much of the original was dedicated to WHY it was better to do the skills neutrally buoyant and in horizontal trim. Most of that material was cut out, leaving an article that told how to do it without explaining why. A key point in those excised materials was that teaching on the knees was teaching how to do things wrong initially with the theory that the skills could be corrected later.
This violates the law of primacy, an education principle that says the way you learn things first is most likely to be the way you will continue to do it. Karl and I had quite a debate about it over the weeks we negotiated our way to the final draft. We finally compromised, and there is a sentence in the final draft that came totally from Karl, in which it is said that it is OK to introduce a skill on the knees first as long as that same skill is later taught neutrally buoyant as well, hopefully in the same session.
Although I cannot say for sure, I am pretty confident that while Karl and I were negotiating that draft, PADI was trying it out themselves and coming to an "OMG This really works!" conclusion. The article was published 6 months earlier than they had originally scheduled it. A year or two later, I wrote another article that was slated for publication but got bumped and never made it. In that second article I went through all the key skills and showed how they were different when done neutrally buoyant and why it was fundamentally wrong to teach it on the knees first. Again, Karl worked with me on the final draft, and in that article, my first draft was accepted with nearly no change, with Karl totally agreeing with with concepts that contradicted his previous opinion.
