In Manx folklore, the water horse that can appear as a pony and lure people is the Glashtin, also spelled Glashtyn or Glashan.
The Glashtin is a shape-shifting supernatural being associated with the Isle of Man. Some accounts describe it as a goblin or hairy sprite, while others identify it with a water horse that emerges from lakes or the sea. In equine form, it may resemble a grey colt or pony, allowing it to approach people without immediately revealing its identity.
Later Manx tales give the creature a more dangerous shape-shifting role. It may appear as a handsome stranger but betray itself through horse-like ears. One story says it tries to drag a woman to the sea, but a rooster’s crowing forces it to flee. Other traditions describe the Glashtin as pursuing women or drowning people.
The Glashtin is easily confused with the cabbyl-ushtey, the Manx water horse, and the tarroo-ushtey, or water bull. Historical sources disagree about whether these are separate beings or overlapping descriptions, but the Glashtin is the canonical answer for this Manx pony-like lurer.