You learn very quickly what is appropriate and inappropriate, depending on your audience. The majority of naturist resorts are family oriented, and all are patrolled to keep away voyeurs and sort out anyone who is acting in suggestive or crude manner. Anyone staying at a naturist resort who made any overt sexual gestures or inappropriate remarks in a public situation would be asked to leave. One of the benefits of nude recreation is that it takes place in a non-threatening atmosphere, where people are free to relax and be themselves. Naturist resorts share many similarities with other kinds of resort, the exception being simply that clothes are optional for most of the activities happening there.
Naturism is meant to be freeing and relaxing.
If you live in the north of England, for instance, then a long walk through the woods nude in the middle of January is probably not a good idea. Similarly if you are at sun resort and think your skin has had enough sun for one day, you won't be thrown out for daring to put on a T-shirt or a hat. Some sporting activities may even require the use of protective clothing. There are no circumstances in which it is mandatory to be naked, and naturists are not campaigning for a clothes free world. They just don't see concealment as a valid reason for wearing clothes.