I have to admit that of all the manimals I find mermen the most difficult to fathom (no pun intended.)
Little Mermaid makes no real logical sense to me and, as far as this discussion is concerned, logic will be paramount.
Take a look at your standard issue mer: They have the upper body including arms, hands, head and face, eyes, ears, nose, mouth, and hair of normal land-dwelling humans. The lower half is scale-covered with a layer of protective mucus and ends in a tail like a fish. Everyone knows the features as art is rife with them.
But this conception is completely ridiculous because it couldn't work as an amphibian being. Centaurs, satyrs, nagas, etc., can work because they are air-breathing land dwellers. But mers are denizens of the seas and waterways. How could anything with the features of a human exist in the sea 24/7? Impossible. Especially, when you consider they have no gills for breathing air in water. Their noses aren't designed to function in water, nor their ears. Their hair would rot off after a while just as their skin would become so liquid-saturated it, too, would rot away. The skin would have to be incredibly thick to withstand the temperature changes of the water and the classical mer is woefully lacking in a design that could handle water pressure as it swam to greater depths.
These are just a few of the many reasons I believe that, if there is anything like a water-dwelling race, they are nothing at all like the popular conception of pretty and handsome fish-tailed merfolk. Hunky guys with fishy tails are a wonder to behold, but anything more than an image, at least on this plane of existence, is preposterous. The closest anyone will ever come is a neoprene tail attached to real human legs. It would be impossible to graft a large fish tail to a human torso and get the blending to survive in water.
However, if some radical changes to the idea of mers went into effect, you could well imagine an aquatic being along the lines of Abe Sapien in the Hellboy Universe. Abe has most of the features a humanoid fishman would need. He has large eyes with sophisticated lenses and lids for bearing water pressure and seeing in the dark. His nose is flatter and has nostrils--gill slits--designed to take in oxygen from the water. He has gills on his throat for functioning underwater. He has no outward ears or body hair. His coloring fits that of sea animals who are marked and colored for protection from predators. His hands and feet are webbed and his fingers end in something akin to small claws. His skin is thicker and has a coating to protect it. He is designed to tread water and live in a marine environment and, in a manimal way, he is attractive on his own level but not "pretty" by the standards of Ariel, The Little Mermaid, and her mer family. Abe makes sense to me. Ariel doe not. Abe can be. Ariel can't.
I am sure that some will argue that I am discussing a mythical creature, something that is merely a fantasy and never existed and never could have existed. But we manimalists take our supposed mythical beings seriously.
I, for one, have always believed that if you can imagine something--whether a nuclear holocaust or flying or dragons or space travel--that event, action, thing or being exists somewhere. Not in our somewhere so far, but somewhere; on another parallel plane, in a far off distant quadrant of this Universe or, well . . . somewhere else. If you think of it, it is on some level in space and time. We create our world whether conscious in the creation or not. So, thinking that, I would suppose that classical conceptions of mer do exist. I just don't believe they could exist within the physical parameters of our world. On another plane, possibly. Just not here. I do believe that evolution could have created an amphibious being--a sea monster of sorts--who became to the marine environment what humans are to the land. The fact that we have never encountered proof of one doesn't necessarily mean they don't exist. The mystery around the incidents in Roswell, New Mexico could make a person believe that aliens may indeed exist but, for reasons of security or to maintain status quo, the government has hidden facts from the general public. This is the idea behind Abe Sapien. Like Hellboy, who is a much more unlikely being, Abe has been hidden from the public both to protect him and to spare the ignorant savages from panic.
I would hazard a guess that there may have been life forms on this planet that there are no physical record of who predated man by hundreds of thousands of years and among them were beings that may very well have looked like crosses between later man and fishes but, in reality, were unlike Ariel and far more possibly like Abe.
I'd be interested to hear what you think a merman would be like, rather than just an sexually-objectified hunk with a tail. Do you agree that classical mers are really only possible in fantasy or have you found reasoning that makes you believe they could and, perhaps, do exist?
I would love to see a real live merman in the classical mode someday. I just don't for a moment believe that will happen. So, through, "Merman Mondays" I will maintain the fantasy knowing fully well it makes little to no sense at all to me. But then the fantastic doesn't have to, eh?
Above art by Ivan Chan.