Regina: "Fillet the fish."
Me: "I have to have mermaids in Calhortea!"
And that's how I got my merfolk. Not that Regina's line actually had anything to do with it, I just thought it was funny. And I found mermaids suddenly intriguing enough to want them in my own books.
Now, I didn't want my merfolk to be like the ones in Disney's The Little Mermaid. I don't know why, I guess I just wanted them to be more intriguing. I also didn't want them to be creepy and evil like the one captured in OUAT or the ones in Pirates of the Caribbean: On Stranger Tides. I really didn't like that version of mermaids, or that movie either, but that's a bit beside the point. So I set out to make them my own. How unique they really are I don't know, you be the judge of that.
My merfolk are about the same size as humans and can exchange their tails for legs at will. (Just imagine how much Ariel would have loved that!) They can breathe both water and air. They actually do breathe the water into their lungs which I guess somehow extract the oxygen from it. Their skin is always moist, whether in the water or out of it. When out, it looks as if they are sweating, which does look strange in the wintertime. Also, their only hair on their entire bodies is on top of their head. Merfolk, um, don't actually have a page in my worldbuilding binder, so I don't know what their average lifespan is. How about two hundred years? That sounds good. Hair and eye colors are pretty much the same as humans. And they don't dress immodestly. Actually, when they transform their tails into legs, their clothes transform accordingly as well. Don't ask me how they do it. Merfolk are smarter than me. But they aren't magicians.
Merfolk are very smart. They are engineers of unbelievable talent. They were able to create a genetic restraint that keeps people with certain DNA on an island (and certain others off) in a world that has not yet taken the concept of the cannon and miniaturized it into a hand held gun. Come to think of it, the merfolk are probably the ones who invented the cannon. I won't talk about their incredible engineering of The Crossways since I want it to be a surprise, but rest assured, it's pretty cool.
Unfortunately, for all their being so smart, the merfolk are so easygoing they're easy to enslave. The strytes most definitely took advantage of that. In Chalton, the merfolk are forced to do manual labor in the coal mines. In Calhortz, they do plantation work. There is a small village in the Yatachee Islands, and I would not be surprised to find an underwater village somewhere as well. Though they are so easily controllable, they do not do everything they are ever told. Rather than destroying all chance of rescue for the rightful king of Calhortz as they were instructed, they made sure that it could happen eventually.
Merfolk are actually kind of background workers. They're not prominently featured in Time Captives, though they play an enormously important role in the backstory, and have a part in the present story as well. I would love someday to write more about them. I still want to write a pirate story about Captain Jeremy Herb's son. Maybe they'll come in there.
On an unrelated note, Sarah Holman's Cinderella short story A Waltz into the Waves is currently free on kindle. Go pick it up! The free promotion ends soon!