In the world of real life is freaky, check out the olm, which even has a name suited for a fantasy.
The olm is a Europe’s only cave adapted vertebrate, and has numerous adaptations for an underground life. Olms hunt their prey in the absolute dark and have developed a powerful sensory system of smell, taste, hearing and electrosensitivity. Olms are pale and sightless, although their skin-covered eyes are still light sensitive. They are an entirely aquatic species that can survive without food for up to 10 years and live to an age of 58 or more. Part of an ancient lineage of amphibians evolving independently for 190 million years, this species is now threatened by pollution and habitat disturbance. A small subpopulation of “black olms” may be a separate species requiring additional protection.
via EDGE :: Amphibian Species Information.
If interested, the olm appears in a PBS Nature episode: Land Of The Falling Lakes. To see the olm swimming is absolutely unreal.
I will have to check that out.