C'mon... you know you've wondered. Artist Walmor Corrêa answers that question in his series of anatomical drawings of mythological creatures. Also featured: the Cyclops, the Penguin and Spiderman. If you're intrigued, you'll probably enjoy his other work as well - I love the "specimens" he has created that look like they would easily fit in a Field Museum if they were real creatures.
Link
http://www.comedycentral.com/videos/index.jhtml?title=mermaid-mating&videoId=156737
i have been researching about mermaids for the past 20 years and i have had encounter. what people say about mermaids is all crap, of course they do exist. If you want to know more, contact the author, of the "The unsaid" on the above e-mail.