for the 'bubbles/breathing" sounds what i ended up doing was getting a nice couple of minutes (no ancilliary sounds like the pop of o-rings tightening up or clunks of the retractor bumping the camera etc) and then i made it into a loop that i play at about 50% normal volume in the background.... that way it's there, but only during the 'quiet' parts of the music (and therefore ususally at the beginning before the music kicks in) nobody has ever noticed that the bubbles in the video don't match the bubbles in the audio.
the MAJOR benefit that this provides is that i import WITHOUT the sound in PPro. that way PPro doesn't have to 'waste' its time during editing doing that &$*%&% CONFORMING AUDIO of audio that i'm gonna turn down 100% anyway. in the editting process i import that 1 little LOOP and the various musical scores.
Good idea, might try that on the next edit to see how the effect goes.