Waterhorse Dragons received their name due to their horse-like physique and endearing behavior. They are capable of surviving out of water, and when on land their skin secretes a gelatinous goo to retain moisture. However, their large paddle feet are better suited for swimming, and waterhorse dragons tend to move very awkwardly when on land. Waterhorses are very friendly dragons and enjoy playing with humans.

Dragons are highly-intelligent reptilian creatures that—from a human perspective, at least—appear to live forever. Many different varieties of dragon exist, each with their own unique qualities, habitats, and behavior. Adolescence in dragons is usually marked by the growth of a hatchling’s wings, although not all breeds of dragons grow wings and some breeds have other traits that indicate the beginning of maturation. In Galsreim, dragons and humans coexist peacefully.

Her Japanese epithet "Ryuuekisei" or "Dragon Liquid Star" in English shows that she belongs to "kaia-chan's scroll". Undine is named after the female water spirits, meaning "wave".

Due to bad experience, she avoids the land and stays in a lake. There are rumours that she left her lake once to go to the ground. Because of her awkward way of walking, the other dragons laughed at her. Whether the rumours are true or not is unknown, but if they were, then it would explain her behaviour.

Undine enjoys playing with human children or to help humans to obtain some fishes.