I certainly do believe they are real. I believe many mysteries live beside us, but we are oblivious and not aware. And also Meerjungfrauen are awesome :P
it is clear to see that humans created Meerjungfrauen from sea creatures that are alike with the Meerjungfrauen tail......I mean a Meerjungfrauen and a dolphins tail doesn't really have any difference in looks...so I don't think they exist....Half human half fisch :/