As you can see from the screen shot, I fell through the ground and got a little wet. I had just jumped out of my valk when I noticed I was falling. It may have just been a fluke, but I figured even though it was funny to me, that you should see it. View attachment 2188
I've actually found a couple places where this happened in the last week. One difference was that I didn't fall. Maybe I stopped just in time? Once I got back out (walked backwards) I couldn't get the issue to occur again so I figured it was probably an issue on my end. Now that I see this I'm not so sure. I only made note of the first location. It was within about 5-10 meters of 19586, 16406.
That also happened to a friend of mine who was riding in the passenger seat of my valk. I hit a tree head-on and flipped the valk over so they were sticking through the landscape. After I picked up the vehicle they fell down into the abyss. If it happens to anyone, just hit "t". Walking or swimming through to the correct side or relogging also brings you to the surface.
It's a bug of the game engine that sometimes allows you to get under the surface (geting out of vehicles are way it happened most times to me). Once you get under, you will keep falling, one time I left it while watching tv and it got under very far under, then I press T.