Good work Bobby

The only suggestion I could give at the moment is to reduce the roughness of the water and set the "ray detail multiplier" to 1.
At default this is set to 0.25, which means that if you render with detail 1 then the refracted surfaces are rendered at 0.25 x 1 = detail 0.25.
So with this setting set at 1 then your render at 0.75 would make for under water surfaces also be rendered at detail 0.75.
Beware this bumps render time, but I suppose you're also familiar with Dandelo's masking method for water, right?