Sometime in the late 1980s, I was riding with a M1 tank platoon that was in a wedge formation, across open ground at Hohenfels. Of course, there was mud and water everywhere, which was a permanent condition there (while you simultaneously choked on dust, of course!).
All of a sudden a tank just wasn't there any more. The platoon stopped, we looked back, and there's nothing but an antenna poking up out of the water. The tank had driven squarely into a flooded basement, and came to an "abrupt stop", as they say.
The crew got out just fine. The tank took a couple days' worth of work.