Oh wow that’s interesting! The water mesh override having any effect is wild, considering it wasn’t changing the terrain beforehand. I can’t replicate these issues for the most part, so working with them is gonna be a tough one. It seems there’s some odd inconsistencies with heightmapped terrains in world partition, but I can’t force it to happen on my side regardless of configuration.
Is the water layer above or below any other map inside the landscape tool?