Found in Version:
This is actually probably a really old bug but I was hopingi t was fixed by now.
This pool of water is southeast of Dun Akafell and isn't actually interactable by the player which is kinda strange since you can actually go below it..
Edit: found the coordinates.
Mephalan Vales Region 28,-14 and it actually is just southeast of Dun Akafell.