Sounds like aquagenic pruritus, I've also had it for years, no cure just learned to cope with it.
Your lucky if its just your legs! I itch from my boobs , down to my toes. Its terrible. And when im in class, and start itching. Its so hard to wait. But if I dont scratch, it burns!
No u not the only one :) my legs itchy as well and i hate when that happen when i'm out i literally stop on the street and start scratching my legs :) must look so wierd lol