"Mermaid" is based loosely on the classic Little Mermaid fairytale.
The original fairytale is about a young mermaid who is a wonderful singer, who wanted to see the sky and meet humans. The song depicts how the mermaid falls in love with a boy who loves the magical stories in books. He wanted nothing more than to meet one of the creatures and followed what was said in the books to eventually discover the mermaid. The boy declared his love for her, but the mermaid knew that he "loved" her only because she was a mermaid and he would have loved any other mermaid.