Harry Potter Headcannons

Chapter 77

Headcanon that since the Slytherin common room is under the lake there's a room where the walls and ceiling are glass and you can just see into the lake like an aquarium.

Headcanon that when this was first done the mermaids got really aggressive and hateful about it and started ramming the glass but since it was magic this just caused them injuries.

Until a deaf Slytherin started to teach them sign language and it took a long time bit by the time they left Hogwarts they and the rest of the house were communicating with the mermaids and on good terms.

Eventually it becomes a part of Slytherin house culture. You're a slytherin you know sign language because if you don't chat with the mermaids they get grumpy.

This helps a lot of deaf students.

This also gives Slytherin the best grades of any house on all aquatic magical studies.

The mermaids give terrible dating advice do not trust them.