Does anyone know the title or author of this fantasy book?

Question

OK. The main charecter's name is Ariel and she has red hair. (Not the Little Mermaid.) She sails across a sea of dust and finds a lump of ambergris on the shore. I think the dust was blue. While at the sea she finds this shrimp thing that later turns into a glowing butterfly while she's in a dark tunnel. She falls down a hole in into a dwarf(?) kingdom. On the cover of the paperback I had there's a girl with red hair holding a lute. That's about all I remember. I read this books years ago and I would really like to find it again.

Not Piers Anthony (Xanth). Thanks though.

Answer 1

piers anthony ? might have had one like this story

Answer 2

Xanth books.