Pearly White Double Tailed Nixie by @BlackUniGryphon (Black UniGryphon)

I don't count it as nude, since it's a fishy being, and no nipples. Just human-like form, but not actually human.

I kept the sketches rough, to keep more that sense of the feel I was going for, and kept the focus on the colors.

The actual sketch should be rough, since it's more the concept, than the refined masterpiece.

These are called all kinds of things: Double Tailed Mermaids, Melisine, Nixes, Nixiese, Undines, Water Nymphs, and so on... everyone seems to have a different opinion, based on their culture over what it's called.