[¯|_(ツ)_|¯]

There might be issues with you two being minors, depending on the laws in your area. It may or may not be illegal for them to see you nude, but that depends on the rules for your location.

As far as morals or it making you a bad person, you're okay for being nude on this beach. You're not a bad person for doing it! I think people who prefer going nude and have that as their lifestyle don't see bodies as sexual the same as a lot of people who wear clothing all the time. In general, people who are nudists see bodies as natural rather than arousing.