To see a mermaid in your dream signifies the female aspect of yourself that is mysterious and secretive. It may also show a fear of sex. In particular, for a man to dream of a mermaid, it indicates that he is having fears of being drowned by the feminine aspect of his psyche. For a woman, it suggests doubts over her femininity.
To dream about a shelled necklace with the word “mermaid” etched on it indicates that you are not letting your vulnerabilities show through. You are putting on a tough facade. Alternatively, the mermaid may symbolise something very personal to you.