Hi, Brian!
I tried to make a plane right under the water now, but nothing happened. However, I started a blank project, imported the same landscape, made sure to add exponetial height fog, atmospheric fog, skylight - and pretty much the same setup as in my original project. And now it works fine!?
https://dl.dropboxusercontent.com/u/18676107/PublicWarehouse_2015/new.jpg
I also added a fresnel in the opacity, which gave almost the same result as in the vRay example =) It would be cool to have a checkbox for this in the future though 