Okay, so I've been looking for the past few hours without luck. Maybe someone can help.
I remember a monstergirl manga that we used to have here on fakku that involved a guy who only had the goal of having sex with a monster girl from the ocean. He sees one in the water and tries to capture it so he jumps in and injures it. Turns out to be female, sexual intercourse ensues, and then we flash forward to the monstergirl feeding her babies. The best description I have of the monstergirl is that she had tentacles and 2 sets of eyes (One set human like while the other like a squid).
Also, before Fakku had changed out of being free, the character had been used as the thumbnail for the monstergirl tag.