Mermaids can be found inhabiting almost all temperate, sub-tropical or tropical coastlines. These legendary creatures are reputed both to have access to lost knowledge and for being good singers.

A certain group of mermaids lived at the place where the Frigid River (Eastlands) poured into the Great Sea during the Second Age of Magic. If there was a particularly nasty bar fight somewhere in Port Foozle which resulted in the death of one of the contenders, those who wished to remove the evidence often dumped the bodies in the Frigid River. These mermaids were known to rat people out in exchange for a big enough salmon.

A trio of singing mermaids (rumored to be "pretty good singers"), which were sought by adventurers on the Tidal Flats during the Great Monster Uprising, were kind enough to translate sheets of music for adventurers. It is unknown if this deed was done for charity or as a service.

The original physical incarnation of Implementor X was that of a mermaid.