Nudism is - quite vocally - not a sexual activity. But is it a sensual activity? I would argue that - strictly defined - yes, it most certainly is. Just by its own nature: shedding the layer of clothing that normally separates you from the world around you introduces a heightened sense of tactile awareness of one's surroundings, making it an experience that is highly sensual - not in terms of sexual contact, but rather in terms of contact with things in general, through your sense of touch.
Sure, nudism may often be a rather mundane activity. You do whatever you would be doing anyway, except you do it without clothes, because it's just more comfortable (or convenient) that way - because you don't like the feeling of having clothes clinging to, or hanging off of, your body. But at its best, in the most sublime moments of nudism, you are uniquely aware of the sensual experience of being in closer connection to your surroundings, and being free and exposed to the natural world.
This is going to sound counter-intuitive (if not downright offensive), but I would be more comfortable if I saw more semi-erections in nudist venues. For men, one of the primary concerns about engaging in nudism is what to do if an erection pops up - knowing that open displays of sexuality are frowned upon. Nudists tend to shrug it off, rightly saying that it's rarely as big a deal as you're liable to make it out to be. And yet, even though I am no longer a complete newbie to the practice of social nudism, it does cause me some level of anxiety.
Yes, it's true, that when you're focused on other activities, and particularly if your nerves are feeling the pressure of wanting to make a good impression, your member is much less likely to spring to attention. But does that mean that it never happens? How about after you've gotten comfortable, when you're relaxed and off guard, and you happen to find yourself in a moment of sublime enjoyment of the tactile sensations on your body? What if some unexpected pressure is applied to just the right spot, or some unplanned motion stirs an involuntary response?
There's a stereotype about nudists that they're mostly older men. My experience has been that the genders are actually more mixed than I would have expected (certainly from the online nudist presence), though there's a question of how much of that is staged (by gender quotas at nudist resorts), or driven by the male interest in nudism (men persuading their wives to join in). Though, there does seem to be a skew toward the upper ages, only partly balanced by the occasional presence of children. And there's a conspicuous dearth of young persons from around the age of adolescence (said to be caused by the unfortunate embarrassment and body consciousness that puberty brings) to young adulthood.
That's a whole different issue to tackle, but the reason I bring it up is that - and I apologize if this is a gross mischaracterization of the older population - some people may not have much of a problem having inappropriate erections at inappropriate times, particularly if they have enough trouble working up an erection when they really want one! Not everybody is in this situation, however, and there are people like myself (whether young and virile or not) who may be highly sensitive to tactile triggers and responsive to the psychological condition of being free and exposed to the world (this may skirt the issue of exhibitionism, but that's a far more nuanced topic than it's given credit for).
I regret the inconvenience it causes, but, to choose one example, spinning a hula hoop around my waist has a tendency to get me hard. After a while, if I stay focused on the task, it will go away. But at the start, I can't help involuntarily responding to the sensation of thrusting my hips in an enthusiastic manner. Nudists tell you that if you get an erection, you ought to hide it and not flaunt it. This is common sense advice, but it's not always straightforward how to go about doing it. For example, laying on one's stomach, if one is not highly disciplined, can serve to actually encourage an erection (by means of pressure). In the hooping example, if I were to stop, and hide myself, I'd never get past the initial phase after which I could continue hooping without trouble. But to get to that point, I have to spend some amount of time swinging my engorged member through the air. Wouldn't that be considered "flaunting it"?
Another issue that comes to mind is that hiding and discouraging one's sensual enjoyment of nakedness could very well significantly dampen a person's enjoyment of their nudist experience. Nudism tries very (too?) hard to be nonsexual, but the problem comes in trying to define what does and does not constitute "sexuality". Most people, I think, see arousal as a precursor to sexual activity, but I don't necessarily see it that way. Getting a boner is not sexual activity (nor necessarily proceeds or engenders an expectation for sexual activity), unless you'd like to suggest that I was having sex in the middle of my eighth grade history class on an irregular basis (you know, them crazy hormones).
Is it possible to separate sensual enjoyment from sexual enjoyment? I think there's a huge difference between your body showing signs of physical arousal in response to environmental triggers, and sitting there stroking yourself while you fantasize about sex. We can't tell what people are thinking about (and not everyone with a boner is thinking about sex), but there's that huge difference between someone who's hard just because he's having a good time, and someone who's actively encouraging his erection through direct means.
Can't we see the difference between the state of arousal and the act of sex? Don't nudists often complain that textiles don't see the difference between the state of being nude and the act of behaving in a lewd fashion? Why does the presence of engorged tissue in a particular part of the male anatomy (a state) cross this line, when a much clearer crossing point would be the direct physical manipulation of that tissue (an act)? The arousal is no more evidence of sexual behavior than a sexual fantasy that exists only in one's mind. It's only after one chooses to act on the thought or the feeling that it crosses into deliberate behavior.
As it is, I know the whole "what if I get an erection" problem is more of a psychological concern than the reality of it warrants. Nevertheless, it's something that a lot of people think about and a lot of people worry about. There are certain activities, that could be very enjoyable for me, that I am afraid to engage in on account of what might happen. As I said, nudists say it's not a big deal, but when was the last time you saw someone sporting a semi at a nudist venue and everyone ignored it or laughed it off? It's all about hiding it as quickly as possible so as not to give the wrong idea.
If I saw a few of them every now and then, and could observe that no one was getting upset about it, I wouldn't care so much whether or not one happened to pop up, knowing that my resolve not to behave lewdly was enough to prevent embarrassment. Getting hard is an involuntary biological response to a trigger, which may or may not be deliberate, and is not something you can willfully and directly control like the flexing of your bicep (I understand this is a difficult concept, as I can recall a heated discussion on this very topic between some of the students and the teacher of my 9th grade biology class).
I'd just like to have the comfort of knowing that something I can't control doesn't stand the risk of ruining my reputation and, to extrapolate to the worst case scenario - especially if it happens in front of unsuspecting women or, worse yet, poor, defenseless children - get me ousted from the club for lewd "behavior". I mean, there are nudists who think it is never appropriate to even sit with your legs apart. In a truly nudist society, we would see these things, and we would get used to them, and understand that they're natural, and nothing to get alarmed about.
I have one final note on the distinction between sensuality and sexuality. I know it's tempting to view arousal as an inherently sexual phenomenon, and hard to view it any other way. We engage in sensual experiences of various types with other people all the time. These are not people we are (necessarily) sexually intimate with. Have you ever sat in a hot tub with strangers? Had a delicious meal with family? Gone skinny dipping with friends you weren't sexually interested in (like, for example, other guys, if you were a straight male)? Or gone to a spa with your girlfriends? Most of these experiences don't cause people to get hard in most cases, but what if it did? What if stripping off your clothes and diving into the lake got you excited, despite the fact that you're not about to have sex, and aren't in the company of anyone you'd want to have sex with? It doesn't mean you're suddenly a sexual predator, looking for a target. It's just a natural, physiological function that we put far too much weight on.
And putting that weight on it is what causes this neurotic anxiety that results in far too many men worrying and asking about "what happens if I get an erection when I go to this nudist venue for the first time". If you're a nudist, and you're sick and tired of hearing this question, the best thing you can do (if you're a man), is to sport an erection the next time you go to a nudist resort. Don't flaunt it, and don't encourage it, but if it happens to pop up, don't hide it. Just let it be. And everyone else who sees it will thank you, not because they're sexually interested in you (although one or two of them might be, but who cares?), but because they'll all be that much more relieved about what would result if the same thing happened to them.
Of course, if you're in the mindset that you would quickly and happily ban anyone who acts in such a way from any nudist resort you visit (or perhaps are in charge of), then here's the effect of your actions. You're getting rid of everyone who has a healthy attitude toward sexuality, while keeping everyone around who is uptight and sexually repressed. Your fear of total sexual abandon is totally misplaced in the healthy subset of the pro-sex population. A healthy approach towards sexuality does not mean having sex everywhere with everyone. That's just as unhealthy as being so uptight that you never have sex with anyone, except maybe in the dark, under the sheets, behind locked doors, with your spouse, while shouting down anyone who ever dares to speak more freely and openly about sex than you feel is decent.
A healthy approach to sexuality means treating sexual arousal, outside the context of deliberate sexual intention, largely in neutral terms (with a lean toward feeling good for another person's enjoyment, rather than jumping down their throat for being "indecent") when it is not also accompanied by inappropriate sexual behavior. Once again, there is a huge difference between enjoying life, however your body displays this enjoyment, and acting in a socially unacceptable manner. You may as well start punishing people for getting goosebumps, blushing, or having their nipples harden when exposed to cold water.