Castle Knightstone is near KotN priory and it should have lake around it, so it should have c.water and load after Knights unofficial patch. Right?
Also, without c.water Region revive - lake Rumare had an empty pond in my game.
To be sure of Knightstone, you'd need to look at in in Edit, and see if it adds a positive water height value to any of it's cells, I've never seen that one, so I'm not sure. And Rumare might be due to the UOPs C.Water tag, which the consensus is to remove. I haven't seen an empty pond myself, the only one that comes to mind is the little hamlet with the bridge, near the IC market entrance?