A post processing volume with:
1) Depth of Field – I have it focused on the pawn, and it gradually decreases as the distance extends radially. It’s subtle, but I didn’t want it to be distracting. It offers the sense that everything is slightly dulled with the water in your eyes.
2) Motion Blur – again, very subtle, but I think it does well to lend the effect of being under water.
3) Adjusted Scene Highlights/Midtones/Shadows – I did this to reflect the sense of being cold beneath the water, therefore there is a subtle blue hue touching everything.
I’ve also moved the water from the background of the scene to the foreground. Initially I believed it would be distracting, but I turned down the wave effect quite a bit and made some adjustments to the material, including removing the specular map, and am finally satisfied with the effect.