Mermaid Man Costume Diy . It is clear that the mermaid man costume is a combination of colors that exudes an aquatic atmosphere. It is the crew headed by luffy in the anime series one piece. Mermaid man and Barnacle boy costume Mermaid man costume, Mermaid man from www.pinterest.com.au The skirt i used a metallic spandex. Here's our fifth annual halloween costume diy! Give me a chance to wear a suit and here i am.