Tip: If you give a Muncher tile custom graphics, it will still act like a coin when a silver P-switch is active, whether it looks like a coin or not. So make sure to use ExAnimation if there's a silver P-switch in the area.
This patch will allow water bubbles you see in underwater levels to refill the air meter.
This patch will also disable the water bubbles that the player spawns in underwater levels so you need to spawn them with this or any other sprite that can spawn them.
This is a good (and creative) way to refill your air meter, though, these bubbles can only live underwater, you can't have them on "air" tiles unless you make your level to be a water level, pretty much like in original SMW.