I've been to several nude beaches; from the remote, quiet, and often unofficial nude beaches of Norfolk, Devon and Cornwall, where people are fairly good at giving each other space, to the busy official nude beaches like Brighton where you really feel you're on show. My gf and I spent a few hours on the Brighton nude beach and we felt a bit uncomfortable because of the number of men who kept walking past gawping at us. It felt a bit like being an animal in a cage.
The embarrassment thing is in your own head and it really doesn't have much to do with cock size. It's more about your upbringing I think.