I'll save my History Retcon till I know a lot more about the Merm Nation, her people and her history.
It'll be by far the easiest to ensure peace and stability not just between the nations but even with the surface world itself.
MC Charm is mostly just to make sure I find a loyal support base asap. But it'll be nice to have some friends, or even more, down there.
Just one problem. My Mermaid Half-Sister needs to read up on her human sexual dimorphism. That is, of course, provided Mer don't have different gender culture and/or dimorpism.