If you are going to bog..........bog a big 'un
There are three shots here of the incident, so you can get the measure of it. There are more photos of the recovery, but that is quite another story.
This was at a MVT event back in 1987 and I am sure the person involved thought it had been forgotten

It was the Bovvy End of Season on Bovington Training Area, Mike Roberts was driving the Grizzly belonging to his father, Denis, when this ruddy great hole swallowed him up. I seem to remember the drain plugs were removed and that did not help matters.
Richard
PS
(for some reason I cannot post the other shots of this)