Agree on Rob's epic mud scenes (imagine if you could travel back in time and give him a set of 4K cameras and multiple memory cards for them?) - but that wasn't "digging in the ground" mud, that was silt pools created by quarying operations, I think from washing the quarried stone. All quarries have such ponds, which will vary in consistency from fully liquid to fully solid as they dry out.

Rob used to fly over the area in a light plane, identify where the best liquid mud ponds were, and then shoot there at weekends when the quarry workers weren't about. Unfortunately eventually word got round and I gather such places in Texas are now kept very secure with armed guards, which is why no-one is shooting anything quite like Rob's content any more.

See my profile pic for my answer. The Amy vs Vika mud match by messygirl is still the gold standard for a mud wrestling match. The consistency of the mud, the pool depth, the coverage not to mention the constant high energy action during the match is why even till this day it's my favorite mud wrestling match ever!