Although the hippocampus is normally found in the Mediterraean Sea, the merpeople capture a blue roan hippocampus off the coast of Scotland and domesticate it.
A blue roan hippocampus is caught by merpeople
Certainty Stated in canon
Location in Canon Fantastic Beasts and Where to Find Them (book)
Type of Event Wizarding world
The hippocampus has an XXX rating (FB).