On our automatic farm, we have a dispenser system that removes all our crops. However, the first layer of our farm is nether wart, so we had to make a soul sand layer. When the dispenser shot water, it created the bubble texture on the source block as expected. However, when we turned off the machine, the water dissapeared, but the bubbles remained, creating an "air bubble block." The air bubbles preform just like regular bubbles: they propel players and items up as expected.