Very nice again Doug. I really like seeing your work
I was wondering if you have increased the ray detail multiplier?
Default is 0.25, which means that if you render with micropoly detail 1, then you render refracted surfaces at micropoly detail 1 x 0.25 = 0.25
If you increase it to 0.5 you can already notice quite dramatic increase in underwater surface detail.
Expect a significant increase in render time though.