Underwater creatures native to the British Isles, Grindylows were pale green in colour, had sharp little horns, green teeth and small pointy horns on its head. Aggressive towards humans, Grindylows preferred to use their long brittle fingers to strangle their victims, and would occasionally eat humans. Occasionally, Grindylows could be tamed by merpeople to be kept as pets, but for the wizarding community, they were classified as Dark creatures and were best avoided, to be honest. Nonetheless, Remus Lupin taught his class about Grindylows during his tenure as Defence Against the Dark Arts teacher.