I appreciate any suggestions or even links to databases / lists of cartoons i can sift through!
Or if you merely know the cartoon and remember additional details so i can search more...
so far google, bing, yandex and chatgpt could not find it

>aired in europe around the 2000s possibly 90s and (very early) 2010s
>on tv in germany, france, possibly uk and nordic
>set mostly under water
>maybe even a planet covered entirely with water except for tiny rock formations and "man"-made habitats
>the tone was dark(ish) for a kids cartoon
>there were very few character on screen (and implied to even live in this world)
>the characters might have been human or some mermaid hybrid
>the protagonist was female i believe, possibly a princess
>the opening song showed her vibing with this uninhabitable water hell and diving to chill with sea creatures
>the villian was an emaciated, multi-armed corpse looking male
>trapped in some sort of space ship wreck under the sea
>he influenced his surroundings through some sort of mystical influence (or maybe just incompetent side kicks)
>there was some (possibly multiple) mcguffins that each would restore a bit of the villains power and health should he acquire them
>i dont remember if it was drawn animation or 3dcgi. it might have been a mix of both
>even though the protagonist and villain were "enemies" i think i remember them talking or even cooperating on occasion
>over all there was no action packed fighting between them, more a scheming and out-maneuvering each other
>i dont think this show was very popular (scrolled through literally dozens of "top 100 nostalgic cartoon" lists)
>it had little humour and little action, it felt weirdly "adult" (at least comparatively). visuals were not eye-candy-bright either
>i would not be surprised if it was one of those belgian-produced-french-canadian-collaborated-new-zealand-funded obscure shows that bankrupted its studio
>name could be something meaningless like "oceania"
please and thank you