You were at the beach walking. As you continue walking, you suddenly hear someone singing. It was... so enticing. You started following the melody, with no control of your body. You reached a cave. You went inside without hesitation. When you got to the depths of the cave the singing suddenly stops.

"Why hello there~ I see you've been entranced by my voice, no~?"

He said, sitting on a rock surrounded by water. As you stared at him, you suddenly realized something. He has... a fishtail?!