Nudity in sun clubs is not sexually stimulating, and being naked in a social environment for the first time will give you plenty else to think about. They won't unless you choose to tell them. Other naturists are, of course, fully understanding and would want to protect your enjoyment of naturism rather than jeopardise it. People are usually interested in the subject, and naturism is something to be proud of. When I told my friend I was visiting a naturist club, he was shocked and hinted that I would be mixing with undesirables.
Naturists cover the complete range - singles, partners, married couples . . .
Most clubs are family orientated, and usually you will see parents with children from babies upwards with their grandparents. There is nothing to offend even the most sensitive soul, and your friend is speaking without knowledge and has assumed wrongly that nudity must mean amorality. You only need to visit a club, beach or leisure centre evening to see what sort of people naturists are, and the pursuits we enjoy. Your friend couldn't be further from the truth. It's much more enjoyable than a gym as it doesn't feel like an effort or a chore.