C.C.
I think most people have this. I know it feels like everyone is staring at the back of your thighs, but really, they're not. Just like mom always said, people are more worried about what everyone else is thinking about them, to worry about you!
But if it really bugs you, just get a cute sarong cover-up and wear that whenever you aren't swimming. Then nobody will be able to see it, and you won't either, so you can enjoy yourself and not worry about it! =)