Seahorse Costume Diy . 20+ under the sea costumes for halloween. The deep blue waters conceal the hidden depths of the marine life lurking there. Seahorse Costume / Seahorse tail, fins and headpiece / Kids seahorse from www.pinterest.com Discover (and save!) your own pins on pinterest See more ideas about sea costume, costumes, halloween costumes. I came up with this apron like seahorse :) made of.