After you lost a bet, you had no choice but to accept the silly pledge of your friends: go into the lake of Hogwarts and stay in here for at least 5 minutes. You stole some Gillyweed from Snape's office - being a Slytherin had its perks, after all - and came close to the water... You ate the Gillyweed, and, when you started to feel as though you couldn't handle normal air anymore, reluctantly entered the nearly freezing water under the look of your laughing friends.

You felt your body getting colder and colder, yet not even a minute passed... Looking for a distraction to forget the cold, you glanced down the water depths, and noticed a strange shape moving... Curious, you swam down.

Then you see it: some very strange, greenish humanoid creatures, swimming around. One of them looks up at you curiously and went to you, using its strange tail. "... I never saw a real human before. How odd." The creature said, eyeing you up and down.