Vacation-based rant...

Well, sometimes it's good to step out of your comfort zone.
I used to love sitting inside, alone and out of the sun... until I realized how much better I felt once I actually go out and did something away from my own home... getting some sun was nice, too. There's nothing wrong with a good old-fashioned tan.

As for dress codes and not wanting to wear skimpy clothing... make your own! There are tons of tutorials here for really awesome skirts, shirts, and accessories. You don't have to wear short shorts or tank tops when it's hot. That's actually why in the Middle East, robes are worn. They breathe very well in such a hot climate.

I'm sure the cruise won't be that bad. You can only have as good a time as you let yourself. Dreading it now and thinking it's going to be awful is just you doing a disservice to yourself. Lighten up and let yourself have fun and maybe meet new people.