I saw a program advancing the aquatic ape theory. One of the more interesting facts cited was that body hair on humans lies in a hydrodynamic direction, while on apes, it sticks straight out of the skin. Also, they noted that there wasn't really a natural change in the hip that would allow the full upright posture. As you say, interesting, but unprovable.
I've read these sorts of things from time to time. I've read that this is also an explanation for the extra fat on females...they spent more time in the water (protection) than men and needed the fat for warmth. Also, the female long hair tradition gave the kids something to hang on to while they were in the water with mother. (???)