I was walking beside a highway just across the ohio state line one day about a decade and a half ago.. I was climbing a small hill to the sholder of the road and the parking area when I was just knocked right off my feet. It's a wooded area and it happened so fast I thought someone had shot me.
Sooo.. I laid very still and looked around real carefully.
That was when I realized one of my legs was buried up to the hip in the hillside. Even more frightening was I could swing it underground (and I have LONG legs.. I am 6'3") and not touch a thing in any direction. It swung completely around in a circle without touching.
Fearing the hillside would collapse and take me with it I spread out my other limbs as far as I could to spread out my body weight.. then slowly withdrew my leg from the hole.
I still don't know what it was, but it scared me nearly to death.