Yes, we all do. Same with my friends and their wives. We all share pictures and you can see the thought process we all have when getting together socially. We each are mentally undressing the wives and thinking about sex.

I had similar to what you describe. A bunch of us were at our house for a pool party. The suit bottom my wife had on, when wet you could clearly see the pubic hair mound in the front, and at one point she had a serious camel toe going.

My one friend left and came back and told me he just jerked off thinking of my wife’s pussy. I just told him that was fast and I hope he’d last longer than that inside her.

My wife and I are social nudists at a resort. We have friends there that my wife is comfortable hanging out with; and as they might have certainly seen her naked bending over, on all fours, standing or lounging legs open, squatting, up close, etc...; there certainly is a possibility that it made enough of an impression that it was thought of later on while rubbing one out. And I'm sure that our male friends are also aware of that possibility; especially the husbands with the more "uninhibited wives." Sitting there legs open while socializing is certainly going to make an impression on most dudes. The "visual" of seeing some wives' shaven pussy up close has stayed with me; even years later.

Some would probably enjoy knowing this for a fact. Others figure as much, accept the possibility; but prefer not knowing.

But it would be naive to think it's just men. I'm sure some women have been so impressed by someone's husband's dick that it made an "impression." Women are usually going to be more discreet about rubbing one out while thinking about some other dude's dick. I'm not going to flatter myself; but the way I've seen some wives look at my dick...has made me wonder. Knowing my wife; if she knew, I think it would actually make her laugh...:o

sauna visit
 

My online buddy (more about him here) with whom we shared eachothers wife's photo's really liked to see my wife naked in real life. And of course I was curious to see his wife "life" as well.

So we planned to set up a meeting in a sauna without our SO's knowing about it. Since our SO's both don't like to go to sauna's in the neighbourhood, and we do live 250km apart, it wasn't too hard to find a suitable sauna somewhere in between our villages so that we could hold up some kind of "plausable deniability". The really hard part was to find a suitable date. For instance matching the calandars of our SO's, last minute appointments etc. Overall it took a while to get a date.

But yesterday we went. We texted each other when we would arrive there. The plan was that me and my mrs. would arrive first and he would come in about 30-60 minutes later. It all worked out well. When seeing each other there. Me and my buddy acted as surprised as we could, while our SO's felt a bit awkward. The conversations between me and my buddy are way broader then only our naked wifes. So due to the happy talking between us, the ladies weren't not suspicious. Their awkwardness dissappeared quickly (luckily they can go along with each other)and we spend the whole day nude in the sauna together (except in the restaurant area of course). We both had great views of our nude wife's. Especially when they were laying in the sun with their legs slightly spread, so we could see their pussies (both completely shaven).

My buddy got pretty excited about seeing my wife naked. For instance he had to stay a bit longer in the hot tub because he had a hard-on. My wife noticed it, and allthough he's not her type, she was slightly impressed with his cock.

Yesterday evening, my buddy and I had a short chat about our day together. And when I mentioned that my wife had noticed his boner in the tub and was impressed by it, he got excited again said he was going to wank off on her.
My wife isn't attracted to him, and he had said multiple times that he would never cheat on his wife so probably it won't go further than that. But it's sure a turn on to know he's seen her naked and that he is wanking off on her :D

Strangers too
 

Sorry if it's slightly off topic. I've wanked over most of the limited number of women I've been lucky enough to see at naked spas and beaches. Certainly the ones I've seen close up, particularly exposed and / or hot.

Knowing that most men think the same, it's safe for me to assume that many men have done the same over my wife, in particular when she's been relaxed about her nudity, been OON and/or innocently allowed a view of her waxed holes.