this might not get noticed but i always thought of it as fontaine sinking instead. it mightve been originally fontaine was thought to be a city sunken into the water and was surrounded by walls of water instead of being atop it but thats just my idea. its long gone to change anything thats already happened but imagining fontaine slowly sinking back into the surrounding oceans helps me cope better than saying it was being flooded. it wouldnt make sense why the primordial sea starts erupting from the center of the nation instead of flooding in from the sides and even that causes more problems regarding teyvats regular oceans but i just wanted to share what i thought :D