Take advantage of what you have... some really like/prefer a small one like yours, even (or especially) when soft.

This is always a delicate balancing act at a nude beach. Guys want to keep their dicks slightly aroused so that they look big but they don't want to get a standing up and throbbing hard-on. It's also almost impossible to do. Once you become excited and your dick starts to get big, it's all but impossible to put on the brakes and not go any further. The best solution is to just let it get hard and don't worry about it. Don't play with it or even touch it and don't attempt to hide it. Just continue on as if you didn't have an erection.

As littlecUnt has suggested, a cockring does enhance the appearance of your equipment. It makes everything look bigger. Try one. I wear mine 24/7 everywhere I go, including nude beaches.