The Naiads are a group of mer-folk created by Mantic Games for their Kings of War tabletop game. Originally part of the Forces of Nature army list, they received their own army list in the form of Trident Realms with the release of the Uncharted Empires book.
They are not nearly as hot as Ariel from Little Mermaid, unless you're into trout. You know. In that special way some people are.