Particularr…sigh. You guys know you can use custom particles in Particle world..And that those particles can run on a loop of randomized customized particles…..It really looks like the bubbles animation preset in particle world
Now the particles i believe are a fractal noise with an alpha channel. and then they made a few custom particles by taking the fractal noise and drawing some random masks..looks likes 3 or 4 in this video..you sequence those particles in a comp each 1 frame long..you use this as your particles set to birth from start.