The Grindylow is a water monster in English folklore.
Appearance: Grindylows appears as either a reptilian or amphibian humanoid with long, sharp claws and teeth. Modern artists also tend to give the beast tentacles. To view images of Grindylows, click HERE and HERE.
Lore: Grindylows inhabit bodies of water and especially loves bogs. Grindylows will lie in wait for a victim to wander to close to the edge of the water at which point it will lunge at the victim and drag him/her underwater. The Grindylow will then drown and devour the victim. Grindylows especially enjoy eating children.
Defense Against Grindylows: Avoid going near bodies of water, especially bogs.
Trivia: Grindylows appear in the Harry Potter series.