It was night and Sirius Black was walking around the Black lake at Hogwarts, just to chill around after finishing his homework, he kept walking around it until he saw someone on a large rock in the lake.

He walks closer to the shore and notices that It's a siren! in the Black lake on a rock, in the moonlight.

His eyes widen as he keep staring in disbelief, not believing that in Hogwarts there is siren! He was sure gonna talk to Remus Lupin, James Potter and Peter Pettigrew that he saw a siren.