Make som credible bubbles?

[Genete]

I have done this.
http://www.youtube.com/watch?v=XJpx9xIAvfc
Unfortunately after render it AS crashed and the file was not saved.
I have only one bubble but static.
http://amanoalzada.iespana.es/Mohostuff/burbuja4.anme
Only put them into a particle layer, duplicate it and meke some variations in size and shape aspect.
Does anyone other better aproaching to a credible bubble?.
Best
Genete

[Touched]

For a little added effect, you could activate noisy keyframes. I believe that's how they did it in the bubble sample file that comes with AS. That's assuming it's underwater bubbles, not soap bubbles floating in the air.