Actually Triton is Poseidon's son, so you're quite right. I was inspired by the Pony I ride which's name really is Poseidon.
Looking to your other mentioned points I think we might have a bit different idea of the picture. At first I didn't want to show an underwater scene, the effects I applied should just give it an unsual, not boring look. I see this picture more as a "might be" painting of a horse on a cliff, where water splashes up. For this reason I didn't remove the halter. Because this shouldn't be a realistic picture of a wild horse I think this halter isn't disturbing. Especially not because it's a detailed show-halter to "decorate" the horse. Perhaps this is a problem of the old halter or no halter question in equine photos. Perhaps this doesn't become clear and I should have used the splash better? The fading hoofes I individually can't see. For me it looks like they are stuck into the rocks. Perhaps this also just becomes clear, because I know what I wanted to show?
So please don't missunderstand me. I don't want to find crappy excuses to deny that the manip isn't perfect, there are just some points I personally don't agree with you / can't see like you. But ofcourse I won't stop thinking about them and check them out in my next manipulation
Because of a whish of another commentor I uploaded a small version of the original horse picture and linked it.
For the painted look, I really didn't see that, but I would suggest smudging the horse and putting another effect over the background, but that's just my opinion
And your right, horses are no hobby, they are passion, no matter if you are a rider or just a "fan" (=