Tumblr artist The Nameless Doll really out did herself. Using talent and what appears to be magic, she transformed all the ladies of Disney into magnificent mermaids. Elsa not included, at least so far, because she'd probably only ruin things (by which I mean freeze the ocean, and that's awkward when you live there). Check out the stunning results down below.
Technically her books would be, at best, a bit soggy if kept underwater. But let's not quibble.
Note: Before there's any discord regarding Megara's status among Disney royalty, The Nameless Doll writes accompanying the illustration that "[Meg is] not an official princess no, but I do love all the Disney ladies and thought 'Why not?'" Do you want to argue?!