Interviews with the creators of Finding Nemo said they included three specific things to give the impression that things were underwater:
1) light filtering onto the objects and sea-floor in a 'shining through water' sorta way
2) "The camera thing" that Binary_Moon and LilPuppy suggested
3) Particulate matter spread (somewhat) evenly throughout the water. Perhaps this could replace your bubbles as an indicator of movement?
1) light filtering onto the objects and sea-floor in a 'shining through water' sorta way
2) "The camera thing" that Binary_Moon and LilPuppy suggested
3) Particulate matter spread (somewhat) evenly throughout the water. Perhaps this could replace your bubbles as an indicator of movement?