A mythological creature, often known as the "Sea Horse". However, unlike real world sea horses, this creature has the head and forelimbs of a horse, while the rear half of it's body is some nature of fish.
The feet may be some nature of fins or claws instead of hooves.
A similar creature is the capricorn, which is composed of a goat rather than a horse. In Greek Mythology, there ere also several other fish-tailed animals, including leokampoi (lions), taurokampoi (bulls) and pardalokampoi (leopards). However, these creatures to not have tags here, and are better served with the merfolk tag.