First of all, what a sexy wife you have! Her curves are exciting!
I think we are talking specifically about seeing without them (friend and his GF) knowing, right?
A few months ago, one of my best friends and I took our girlfriends to a SPA (we went together because there was a very good discount if you attended with a 4 person group; otherwise, we'd have gone by ourselves).
His girlfriend was trying (successfully) to lose weight; so her bikini would fit her a little loose. It was not a problem until we got into the pool. Whenever I looked down, I could see her bikini bottom (not a Spongebob reference
) a little off to one side. She didn't noticed, so I kept glancing at her crotch every time I could (and trying not to be obvious).
It didn't take long until I could see her outer labia and then the inner one. It was the kind of vagina that looks like a flower (lucky for me, because that's why I could see it). I didn't have the chance to see her full vagina; but only like a 40% and that was more than enough to masturbate a couple times thinking about her.