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A stretch of beach - seaside or lakeside - where the policy for swimwear either permits or encourages patrons to do without any form thereof in part or in whole. The reasons for such can range from lifestyle (such as Germany's Free Body Culture, to as vain as ensuring universally even tan. A variation is the "Clothing Optional" beach, where patrons are permitted to change to and from nudity as their tastes prefer. Laws concerning such establishments vary greatly from country to country, and even from location to location, so before attending to one, it is recommended that one research into the law to avoid potential legal repercussions of Indecent Exposure charges while attending an illegal nude beach. As such, nude beaches are often privately owned, and take advantage of geographic features or manmade structures to ensure outsiders do not see the patrons.
On the topic of indecency, while the appeal of seeing nude members of the opposite/preferred sex is obvious, in reality many of those attending are not normally paragons of sexuality, and in fact it is common for children to be present as well. Therefore, it is best to consider nude beaches as normal beaches, clothing aside.
A note to gentlemen desiring to seek out a nude beach with the intent of ogling women anyway - while that is your prerogative, bare in mind that blatant creeper staring is just as undesired at a nude beach as elsewhere, if you must, take measures to be subtle. Furthermore, unless you have an uncanny control of your sex drive, a man attending a nude beach in the nude must be aware that an erection is just as obscene as anywhere else. If one cannot 100% control yourself, either wear trunks, get used to the idea of covering oneself until the moment passes, or bring a tent to 'deal with' it.