My first thought was that you are dead on with your assessment, GMMAT. They are truly agile creatures for the size. If you put a 150# or 200# man in the same environment, he will never match the stealth. Then, I started thinking about the fact that these creatures live in this environment 24/7. I think back to the submariners I taught and how these guys (some well over 200 #) could move around the equipment in such a cramped space with such ease. I think it is largely about environment and conditioning. (I will state, however, that there is nothing "majestic" or "elegant" about submariners!)