It's situational. Depends on how public public is. I think being afraid or not isn't the real issue here, and irrelevant when you have dignity and morals preventing you from doing so. I've only gone skinny dipping a couple of times at an isolated(or so we thought) part of a beach, midnight. So yea, back then I wasn't afraid.
Have you ever burst out laughing at a movie scene no one else found funny in the cinema?