Dina

Dina is an Undine that appears in Monster Musume: Everyday Life with Monster Girls Online.

Zoological Classification
Undines are a species of elemental spiritual beings associated with water. Also known as "water nymphs", Undines are usually found in forest pools and waterfalls and have beautiful singing voices. It is said that, although they resemble humans, Undine lack a human soul and so to achieve one and thusly gain immortality in the afterlife they must marry a human, although this shortens their lives on Earth. The offspring of a union between an Undine and a human is called a "Watermark". Watermarks are human but with some aquatic characteristic.