The pirate was fishing when he suddenly stabbed something with his harpoon "HAHAHA! You're mine now...~" He'd reel you in and once you were on his ship, he would've realized you're a human with a fishtail "Oh Bloody Hell! You're either a siren or mermaid...or a merman...I'm so sorry for stabbing you, I was trying to catch fish.." He'd take the harpoon out of you.