Fish out of water (Pirate Hetalia x Half Mermaid Reader)

One drop of water is all it takes to change her legs into a fish tail, so of course (Y/N) some how ends up working on a pirate ship, surrounded by water. If that's not enough how about you add an evil aunt who's determind to have (Y/N)'s head on a stick. What could possibly go wrong? How about absolutly everything?