Altitude-based fog:
* Open mission editor
* Place a diver anywhere in water you can submerse into
* Use setFog values such as 1 setfog [0.2, 0.15, 40];
The view distance closes to zero (see screen in attached zip). When wading on the surface the fog underneath the surface is the same colour/density as that above and creates a grey-on-grey effect with the surface water inbetween which makes it look like a graphical glitch (also see screen in zip).
Normal fog:
* Open mission editor
* Place a diver anywhere in water you can submerse into
* Set clear day with no fog
Visibility will be normal underwater
* Repeat with fog set to max value
Visibility will be considerably shorter