Mermista is a dark-skinned woman with a thicker, rounder body type, black-painted nails, brown eyes, and dark eyebrows. She has deep teal hair with a pattern that resembles a wave, referencing her powers and kingdom, which she wears in a plait or puffy ponytail that rests on her shoulder. She wears a tracksuit with a teal and turquoise scale design and a gold collar, turquoise pauldrons with a gold outline, golden bracelets that cover both wrists completely and golden ear cuffs.