Dispensers taking water away from a bubble column leaves the bubbles and they still move the player. To recreate simple place a soul sand block down and water on top to create a bubble column then using a dispenser with a empty bucket in, activate it and it will remove the water but the bubble column will stay. p.s at that point updating any point besides the bottom will not make it disappear and it can essentially have no blocks around it except for the soul sand.