I got to agree with jumpstartme, perfectn... that's is definitely a nude picture. Please, bear in mind that nudity refers to naked skin, and not necessarily to genitalia exclusively (whether primary or secondry).

Fantastic piece of work, mind. Just as one minor comment, though... would a mermaid's tail really begin that low? Most mermaid images I've seen in the pst tend to have the fishy scales beginning waist-ish area, which kinda makes sense to me... otherwise you have the legs melding together lower down, which would just look very odd indeed! :)

jonthecelt