Let me dig out Oleg's underwater scene. I know there is one in there.
Maybe this?
Here is that setup thrown together quick, cube resized, but it should not matter. I think the key is the large scale power factal before the default shader and the round radius. Example used img map, so I made a quick one and substituted. In the merge I had to adjust to see the mix, but you could probably string PFs together for similar effect. Probably even surface layers...do not know yet.