Most people wouldn't feel comfortable removing all their clothes in public, but for some it's a way of life. American writer Mark Haskell Smith overcame his nerves and spent a year immersing himself in the world of nudism.
"If you're at the airport, you don't make jokes about bombs. When you're with nudists you don't make jokes about breasts. And God forbid, don't get an erection - you will probably be asked to leave," says Haskell Smith.
These are just two of things he learned as he visited naturist resorts around the world.
His first stop was the Desert Sun Resort in Palm Springs, California. "I was terrified. I was there, awkward and anxious in my hotel room, putting on layer after layer of sunblock, until finally, when I walked outside, I was a beacon of light and highly reflective. There are all these people around the pool and they all look at me and then they wince and cover their faces.
"I was really insulted, I thought, 'Hey wait, I'm 20 years younger than all of you people,' and then I looked down… and I got it, I was like, 'Oh dear.'"
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After getting over his sunblock faux pas, he went to several nudist resorts in Europe. Cap d'Agde in the south of France is one of the best-known. Once you get inside the security fence, which keeps out the paparazzi and curious passers-by, there is everything you would expect to find in any other town.
"Except everyone is naked," says Haskell Smith. "There's even a dry cleaner - I don't know what they dry clean though. Going grocery shopping or having your croissant and coffee in the morning in the nude was actually so weird it was kind of fun. And once you've gone to the wine store and talked about the local rose naked then anything is OK."
Hiking through the Austrian Alps for a week, with 19 naturists from across Europe, also proved to be surprisingly enjoyable.
"The air is really clean and you're working hard because you're climbing at altitude but you don't really sweat, so you're not uncomfortable - your skin is this great thermostat for your body."
But when the wind turned cold and the snow started to fall, though, he did reach for some clothes. But other members of the group carried on regardless. He recalls one Scottish couple. "They were just walking down the trail going, 'Look, that pond's got ice on it.'"
If a group of "textiles" (people who wear clothes) came across the naked hikers, most of them would smile and laugh and reach for their cameras.
"But one day we came across a bunch of Christian hikers and their leader made everyone turn and face away from us as we walked past. I couldn't believe it. Then later, when we were having a picnic by a lake, we saw them again and they prayed for us."
Despite gradually becoming more relaxed about being naked in public, Haskell Smith always had last-minute nerves about removing his clothes when he re-entered a nudist environment.
"These fears are really all inside your own head. The nudists really don't care. The people you usually see naked are almost all actors and models on TV and in advertising so we've been brainwashed into thinking that's what a naked person should look like.
"Naked people really look like everyone else so I think the idea of accepting your body and other people's bodies is really healthy. Our society needs all kinds of tolerance and this is a good place to start," he says.
He found a strong sense of community among the diverse group of people he met - from doctors to firemen, office workers to university professors.
- A towel is the most useful thing a nudist can have - it's practical and hygienic
- No staring, it's rude
- Leering and sexual displays will most likely lead to expulsion
- Photography is not welcome except with permission so put your camera away
- Privacy is important and many nudists just give their first names during introductions
"A lot of the nudist resorts that came about in the 50s and 60s are ageing out, they're becoming these naked retirement centres. But there's a whole new generation of young nudists who like to go to beaches and go camping. Almost everyone gets into it because they like to skinny dip. Once you swim naked and you realise how good that feels, you're then willing to barbecue naked, or go on a hike naked."
And skinny dipping in the crystal clear waters of the Bahamas was how he finally persuaded his wife to join him on a Caribbean cruise with 2,000 other nudists.
"It's mostly a couples things, whether you're gay or straight. When you're a single person and you're naked with all these couples they look at you like you're a weirdo. So when I had my wife with me, and perhaps because she's attractive, suddenly we were the life of the party.
"For me, the best part was one night I went to the disco and there was a woman, probably in her 70s, wearing a see-through French maid's outfit. She had her walker and was in the middle of the dance floor just shaking it. I thought to myself, 'It's either the most horrible thing I've ever seen or the most inspiring.' I hope when I'm her age I have the courage to do that."
Haskell Smith's decision to try out the world of nudism stemmed from a fascination with subcultures - and "why people do what they do despite the stigma".
But one year was enough. If he's in the Caribbean, on a beautiful deserted beach with his wife, then he might go for a skinny dip. "But do I want to stand around a barbecue with 100 other naked people? Not so much," he says.
One conclusion he has drawn is that nudism is definitely not about sex. On the other hand, that doesn't mean people never take a good look at one another.
"We're humans you can't help it. Sometimes I'd find myself staring at people and thinking, 'That's what that looks like!' You could really marvel at all the surgical scars, like they were wearing their medical history on their bodies.
"There's nothing more fun than seeing an 80-year-old lady checking out your package."
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