Air Bubble Effect

It's so nice if you already have something that works well and can just enhance it with little effort. That is true for my particle system, so I added air bubbles. MetalBeast kindly provided an air bubble image which I slightly modified to make it wobble a bit, and a sine function made the bubbles wiggle. If you don't like these effects you can easily turn them off in the smoke options render menu (which I should probably rename in particle system options menu ...). Here's a video to show the effect: