It’s never too early to work on your shidduch profile, so….
Sit at the beach and work on your tan 🙂
Seriously, I like Popa’s idea. You can also try bikeriding (as a girl, you don’t have to worry about minyan & the sort).
Another option is to use the money saved by not going to camp on a project, such as rebuilding a car, cake decorating classes, or even sign up for early college courses at your local college.
Good luck.