Sahuagin

Sahuagin, or sea-devils, are humanoid fish-people. They are mostly regarded as a superstition that pirates have. Pirates believe that these horrible fish-man can climb onto boats, that sharks respect and obey them, and that they have all these mystical powers around blood. However, the exact nature of these powers is vague and varies depending on the source: in some stories, they can suck the blood out of you; in others, blood in the water is what draws them to you.

They move in packs, have razor sharp teeth and green froggy skin.

Gail states that's she's never seen one in real life or heard a story that she believes.

The Franks say that the farther north you go, the larger they become. That they're the size of a human and our shape