I vividly remember a few years ago loving a character design, this wasn't a specific character just and aspect of one
I think it was something like aquatail or hydrotail or something like that, the character had a normal/more flesh body but their abdomen and tail were connected and made of a different substance similar to transparent body parts and goo hybrid but not quite that, I think one even had fishes in their tail, if anyone knows please let me know