With the random attacks on the farmlands, it's possible for the encounters to spawn with waist-deep, sometimes opaque water as the terrain and Orcs as the enemies. This leads to PCs being Disarmed by the Berzerkers and having no way to recover their weapons short of swinging the mouse wildly over the area until it goes over the item, or trying some really wierd camera angles. I spent about 5 minutes trying to work out where my PC's dagger ended up.
I've come to find that the relative transparency of water is dependant on the type of graphics card that is being used. So in case someone was going to jump in and say 'you can see it just fine' - well, that might not be the case for everyone.
Having played a Diluvian in the past and spending lots of time in these waist-deep water areas, I can definitely confirm that it is a very annoying thing to have to deal with.
This is no bug.