If you have a bubble column flowing up a water pool and you push a piston into the column as long as it has the requirements for a piston to push a block normal it will push the water into the next block space the water block is just a normal block no bubble effects on it. This doesn't work with normal water. The image attached shows what I did to test it. with the build i did the water block will be destroyed by the sand but if you remove it you will see water being moved though if you do it again into the water block the new pushed water will just be absorbed by the water that was pushed before. Sorry for the long description wanted to put this in full detail and unless I missed it there was no post on this that I saw.