Whats the best way to create random paths for bubble objects?

Hey!

I am looking for the best and easiest way to generate random paths in order to imitate the movement of bubbles under water.
Each object should have its own path and collision detection needs to be possible, as the bubbles should be able to interact with fishes etc.
First i thought UnitySteer might be the perfect lib for me, but since the documentation is really bad, i haven't found a solution for my problem, yet.

thanks in advance!