I've been a big fan of Juan Cabana for a few years now. Almost as long as I've wanted to build a feejee Mermaid. Like the sea, the ebb and flow of the internet seems to be washing up a few oceanus hominum lately, mine is almost finished too. It's no easy task creating realistic creatures but sea beasts are another proverbial kettle and Cabana for me is the bench mark. This is only a small sample of his work but head over to this site for further bounty.
From Cabana's website - "Cabana's mermaids are no gentle pre-Raphaelite maidens. These mermaids seduce us, not with their siren beauty, but with parchment skin and haunted eyes. Their allure lies in their hypnotic honesty. Cabana's mermaids have been dredged from the stygian depths, where the pressure and endless darkness breed spine-toothed monsters and grotesque simian scavengers. These creatures are the sisters and brothers of Barnum's Mermaid, some crawling from the banks of a lagoon, others laid out like wizened specimens in a laboratory. They seethe with life, they call to us with shrill tongues and crooked fingers, they beg to drag us down into the abyss. From the mid-ocean trenches and the bottomless channels they come". - Kim Bannerman