We used to be able to make elevators by placing a magma block (down) or soulsand (up) at the bottom of a 1x shaft, then pouring water at the top, and having it flow all the way down to the blocks, which would then generate bubbles and you could fast travel up the soulsand elevator and down the magma block one. It was a useful feature.

Now trying the same thing, and you get only a few bubbles and no movement through the water whatsoever. What happened?