I'm a male approaching middle age, and I've always been fascinated with the psychology of nudity. I guess you'd call me an exhibitionist, though I would never commit an illegal act of 'flashing.' My masturbatory 'material,' in large part, comes from the idea of being nude in front of women, who may or may not be nude themselves.
I'm a voyeur too, like most guys, and so I like any forum for nudity. When I look at Playboy and other depictions of nudity, though, I think my thought process is different from that of most males. Instead of thinking 'Oh, man, I want to fuck her,' I'm thinking of what's going through her head, of whether she's scared or energized or both at the thought of men and boys and women being able to see her naked and being aroused by her. Scared is more of a turn-on than energized. Women who are 'out there' with their open sexuality are sometimes fun, too, but a lot of those women don't LOOK naked when they're naked, if you know what I mean. If that's their natural state, it isn't much of a thrill. A shy, normal girl with tan lines, on the other hand, is really sacrificing something on the viewers' behalf, and so that is really cool.
Still, I'll take what I can get. Strip clubs are great, and massage parlors, and nudist resorts, but what REALLY turns me on is the rare case of the opportunity for casual co-ed nudity. Nudist resorts are full of people who had to make a real effort to show up, and they tend to attract unattractive people.
On a precious few occasions, though, I've had the opportunity to be in public or semi-public places where clothing is optional in the midst of otherwise normal conventions. One such place was a beach overseas with one small clothing-optional section, another was a public park in Europe with a clothing-optional section, and the last one was a spa in the United States that included a swimsuit-optional hot tub.
The spa experience, a year or two ago, was the most recent. I went for two or three hours on two occasions (unabashedly naked, of course), and I saw probably two dozen or three dozen men and half a dozen women. This place has two communal tubs, one for women only and one for both sexes, and so the psychology of the few women who would join all the naked men is particularly interesting.
In most cases the women were older, not all that attractive, and accompanied by a man. They took off their spa robes easily, and all male eyes turned, albeit discreetly. One woman in particular, unaccompanied, probably in her early 50s and in decent shape but still not exactly anything you'd consider attractive, moved about easily and chatted with the naked men as the only woman there. Does she go home and masturbate while thinking about all that exposure and all those men?
By the way, I don't buy the nudist explanation that it isn't about sex. It's nice to feel the breeze against your body and all, but primarily it's about sex. Almost all male eyes were constantly looking at the door to see if an attractive woman would arrive.
One moderately attractive woman did show up, with her attractive boyfriend. She was the only woman who covered herself at all -- she was topless but wore a bottom. I thought and thought about what she might have been thinking. Was she doing this for her naked boyfriend? Was she getting any thrill at looking at the other naked guys, or having them look at her?
And then there were the bathing-suit guys. Three or four men, all of them on the young side, exercised the bathing-suit option. I thought I saw some tiny glances of disapproval from the moderately attractive woman, but I might be making that up.
It is the idea of imbalance that fascinates me most. A nude woman is inherently more 'valuable' than a nude man, so there's an imbalance right there. Then there's the imbalance in the numbers, and the willingness, and then the idea of a bathing-suited man or a bottomed woman, where you have someone either partially participating or not participating at all in the exhibitionism while at least technically participating in the voyeurism.
Men's heads definitely turned on the couple of occasions when a clothed female staff member peeked in. I recently discovered the CFNM (clothed female, nude male) subcategory of Internet porn -- again, the imbalance. I suppose there's some humiliation fantasy involved there, considering how ridiculous and unappealing a naked male body is. I think my fantasy scenario at the spa would have been to have two or three bathing-suited woman arrive and sort of giggle to themselves at all the shriveled penises.
That did happen, at least in part, at a 'real' nudist camp I visited once. A very attractive woman, who obviously knew all the regulars, arrived and made the rounds, walking around and talking to many people with her clothes still on. To complete the fantasy, at last she did disrobe.
And at the once nude beach I visited, I accidentally strolled beyond the 'nudist' section and drew some giggles of that sort. I still think about that a lot when I masturbate.