The episode with the scientist
I don't remember the exact details but there was one episode where Lewis fell in love with one scientist and she was making a research about something Lewis had, from the girls.
It bugged me how the episode treated the scientist as a villain, she was just doing her job. Sure, she lied to Lewis a little, but she told him everything later and it didn't seem like she planned to trick him or anything. She found something that could be revolutionary, she didn't knew anything about the mermaids, but the girls act like she's evil or something, just because she's a scientist who has something from them.
I know they must keep their secret, but what's with the twisted sense of justice etc.?