Daydream Underwater Experience

Hi there! Wondering if anyone has had success getting near-photoreal underwater shading to work well on Daydream with Unity. Yes, fog and a blue tint looks okay, but I haven't had much success with light shafts, adding lots of bubbles, or filling the scene with, say, schools of fish without killing the frame rate. Anyone have any suggestions on optimizing an experience like this for Daydream? It's most important that what is in the scene looks as realistic as possible, even if that means severely limiting what is visible at any given moment.

Thank you!