Bubbles to indicate air under a solid block

Minecraft already indicates there is water above a solid block with little drips. I think it would be a useful and interesting addition if there were similarly small air bubbles in water above a block to indicate there is air below. I think the bubble size and number should be less than for magma or soul sand; just a subtle slow bubbling. This would be an interesting way for the sharp-eyed player to find air-filled caves when cave diving.