2 issues I stuck at.
The first is...somehow I am not able to create the lightbeams from the caustics. I might have missed something but the only option might be responsible for that is the photon volume in the rendering-lighting-tab which I obviously turned on and played around with.
The second, hmm dont know how to tell..
If I take a look at the picture below it seems that the brightness/density of the water is dependent from the viewers position. It gets more dark and opaque in the background and pretty clear in close range. When I try to recreate this by playing with the density, transparency or opacity it looks like I am getting a constant fog rather than a linear increasing one. If I put the values down, I can see the physical-sun-horizon. If I put them up I cant even see things in close range or in a very foggy manner.
I hope you dont mind my lack of technical terms.
This becomes more apparent with a situation with total-internal-reflection