Mermaid Costume Diy . The tail is easy to walk in, turns into a cute skirt, and this pattern also has a bandeau shell top. She'll never want to take off this homemade halloween costume. DIY Halloween Costume 2 Mermaid Can Can Dancer from cancandancer.com To creating a voice activated light up seashell. Sew a some stretchy scale fabric * into a tube that is the circumference of your child’s hips. The tail is easy to walk in, turns into a cute skirt, and this pattern also has a bandeau shell top.