I have seen that show! I was considering some hydokinetic ability...I was going to have it so that there were merpeople more powerful than others, especially the leader/royalty figures, and since her family are the leaders of their pod I guess it would make sense for her to have some elemental power. But I'll probably have her older siblings be more powerful. But not super powerful ha or else they would have destroyed the human race by now. 

I like the idea of the kiss binding them, too, we should definitely use that. It would be interesting if she didn't know about the binding effect the kiss would have on them, just about the surviving underwater part. And I have done mermaid rps where the mermaid was able to gain legs on land. I'd be down for having that. It could have been a forgotten ability due to them wanting to isolate themselves from humans. I was thinking of having Mara wanting to run away from an arranged marriage a little further into the rp, so the legs thing could help give her a place to escape to. Also her having legs on land doesn't make her quite so limited to the water. I like it. ;)

I also thought that merpeople could live longer than humans. Not immortality but once they reach a certain age their aging slows. But I can toss that idea.