In addition, default camera position is 0, 10, -30 and when SSS is enabled you see the cross hairs of the bounding box for the SSS.
I have elevated my camera and angled right and down to show you the screenshot of the red edge of the SSS circle encompassed is the 10000 meter square bounding box.
In the classic version when we generated terrain, we used fractal generation in a different manner as you recall. Then when setting water level, remember how you used to have to fiddle with the elevation, sometimes 0 was still underground, depending on your terrain. Then you would update your maps .
Also, if you take your camera down (- key on compass navigator) you will see the little red icon, telling you you are under the SSS, but your masked terrain is there under the SSS. If the SSS is disabled, you do not usually get that red icon when descending at default camera position.