These water demons live in ponds and rivers. If you ever run into one, try to trick it into bowing. If a Kappa bows, the water will run out of the hollow spot in its head and it will lose all its power. You'd think they'd know not to fall for that trick by now.
(Harry Potter book shout out: Kappas are found in Japan, but when he substitute-taught the Defense Against the Arts Class in Harry Potter and the Prisoner of Azkaban Professor Snape swore they were from Mongolia. Time to brush up on your Fantastic Beasts, Severus.)
This water demon hangs out in rivers and lakes and can take different forms.
Its main goal is to lure unsuspecting folks onto to take a ride on its back then dive to the bottom of the lake to eat them. Yikes.
The most famous kelpie is the one who lives in Loch Ness. This one enjoys appearing as a sea serpent every once in a while. She's a bit of an attention hog.
Knarls look just like hedgehogs…except they're way more suspicious of people.
If a hedgehog finds food left out, it eats it. If a Knarl finds food, it attacks the family's garden. We feel bad for the poor Muggle children who got blamed for wrecking those gardens.
Knealzes look a little bit like cats, but they're also good at lie detecting and finding their way home when lost.
You need a license to own one, since Muggles tend to think there's something up with these guys. They look a little odd with their giant ears and tails like lions.