The Grindylow is a small, horned, tentacled creature that usually lives
in weed beds at the bottoms of lakes. They normally eat small fish and
algae, but they will eat humans occasionally. In order to defeat a Grindylow, it is essential to master the spell
Relashio, which forces them back. Then, while they are still dazed, you
must be able to snap their fingers, which is the way that they strangle.
Their fingers are long and brittle, so it should not be too hard.