Its basicly a cube 200x200m and 24m height with a volume absorption shader for the water color and scattering shader for backscatter.No world scatter,only the scatter/absorption shader in a cube as domain.
With only one sunlight at 1000 strength.volume bounce set at 12.
Yes i noticed that too,but is very subtle.
Sure, i can render it then.But as @moony meantioned filter glossy at 0 makes not that sence.
The scene can be as difficult to render,but it should have standard rendersettings though.