mermaids
features: one - three horn(s) on their head the same color as their tail, fins on the sides of their face, gills on their neck to breathe (maybe some on their waists as well?), all different kinds of colors, some have lights that glow in the dark for deep water mermaids

fae
features: two grand fae/butterfly wings, always glittery and bright, most potent magic

beach dwellers
features: water for hair/tails/wings, items they collect from the shore, skin can be sand or jelly or anything really, really like human culture and technology