Chaosmancer
Legend
That is frankly a stupid rule, proof to me of WotC 5e's radical oversimplification. It would never fly in my game.
I don't think we should care whether or not you follow the rules of 5e.
Additionally... why is it stupid? I can trivially point to multiple stories of heroes and other people who have swam through water in armor. Is it just stupid because you don't like it?