On a realm world used sand at first to create some walls to safely enter a ruin and obtain items from a chest. Noticed source blocks of water could not be stopped when placing a solid block of any type. When you place the block and remove it even in a 1 by 1 space of water with for instance chiseled stone etc from a ruin surrounding it the water would be replaced but soon as you remove that 1 block water would re-enter and fill it from solid blocks around it. 

Even attempted to tear out these blocks the ruin is constructed of and replace them with eventual success to stop the infinite water source only to have flowing water. Took a lot of placing and replacing every last block of either water or stone to slowly build an air pocket.

What it acted like is as if the Chiseled stone was sharing a spot with a source block of water. So it was as if you had to remove the stone block to access the water block then remove or replace said water block as well.

I do not know if this has been reported or not, I tried to search but since it is hard to define no search showed that was seemingly related. Sorry if this is a duplicate report.