Just get some extra shells an you'll look like a proper upright mermaid!
See, the skirt fits tight around the thighs, and then falls to the floor around the knees, so it looks just like a mermaid tail! No? Now doesn't that feel more natural? For instance, you could wear our Adult Mermaid Costume. Second, get some fish friends. Have you always felt like a fish out of water? Like you just didn't quite belong? You're totally a mermaid, aren't you? Firstly, get some quality water time.