Hi Ann... I've had muscle changes, but not assymetrical... Mine have all been pretty symmetrical. However, my PN is pretty symmetrical. Some of the members here have had some asymmetrical PN, so they can better address your question.
I have gone from a very active athlete to a pretty inactive person. I've noticed that my muscles have decreased a lot. I'm starting to exercise again because I've got my PN under control now, and I am finally able to climb stairs and walk at least 1/2 mile now. I've noticed that the muscles "remember" quickly, and seem to be coming back easily! My brain wants to jump back into the training again, but my lungs don't think they are ready yet!
If I were you, I would have your doctor look at the muscle decrease the next time you see him/her. Especially if you've been pretty active over the last month. Swimming is a very symmetrical activity and doesn't seem like you would favor one leg over the other.
Keep us informed! I would like to know the outcome.

Oh, and what a great way to spend your vacation, snorkeling and hanging out on the beach with your family. What a lucky woman you are! I would love to do that! Water is my "relax" tool.

Terri