What was the deal with the mermaid getting Lily pregnant? At the end, it appears that Lily's daughter is just a normal child, and for some reason Lily felt grateful that the mermaid Queen spared both her and her daughter. But wasn't the point that the child was basically somehow the mermaid Queen's child too? I was thinking that that is how they reproduce. There would appear to be no males of the species, so, they feed on human males, and use human females to reproduce. But the movie never really said that. It was like the pregnancy was a "favor" the mermaid did for Lily (the same way she killed Miles "for" her), because Lily was not able to have children the normal human way.

Of course if there had been a part 2, maybe they would have gone more in the direction I'm thinking.