Just FYI - Not a good question/vary generalizing, rude, etc. Just think about it a little bit.
Nudists aren't diffrent from people who wear clothes, they just don't want to deal with the clothes part. My family knew some nudists and they were just like everyone else. Lack of clothes really would make it easier to have sex wherever but that doesn't mean they do. Still inappropriate to have sex on a public beach, even if everyone else is nude.