Mer Popo
Noun. These are the guys (read: popo) that will come after you if you try (and hopefully succeed in) fucking a mermaid. If caught, you'll be sent to Mer Popo Jail-- there's no place worse on earth/under the sea.
T-Pain wants us to believe him when he says he fucked a mermaid; we don't need his word, the mugshot taken by the Mer Popo says it all.