I would get at the beach at 5:30 PM and it wouldn't start getting dark out until 8PM. People could have cared less about what I was doing? Once it got dark my headlight would come on. People would still be coming to the beach it's relatively safe at night. I just keep a good distance from people if they are lounging on the beach, say 6' + so they don't feel that I am encroaching on their personal space. You do it that way and people could care less what you doing as long as you don't bother them.
When I was there this past Monday I see an old women there and see is reading a book with her Great Dane who could have pulled her like a rag doll if it wanted it to and then she is reaching for a beverage and I look and see she is drinking a Bud Light,heehee. Numerous violations are going on now but officially the season is closed and no life guard is on duty. Surfers are coming in cause it is a decent place to surf as it's kind of a small bay making the waves numerous and fun to ride.
I just make sure I keep my end up so it doesn't look bad for the sport and people basically blank me out. You'll always get smaller children who always are fascinated by metal detectors, people asking questions. I take 5 minutes and chit chat and then I move along. I don't let it get to me like I am in a race and their are disturbing my world. It's all on how you project yourself. Think positive, think Gold!