Quicksand Fans

Today I was fishing at Cliff Cave park on the Mississippi when a few people came down to the creek confluence I was on and began playing in the mud up the creek. I asked one of them how deep it was they said very, one sank to their waist. So, I went and changed shorts to swim trunks, and tried the same thing. It was pretty cool. Only got about upper thigh deep, but I may go back tomorrow, to push farther. It is a county park tho, so there are ppl, and I just say I was fishing, or explorering. Plus Im a bit weary about MIssissippi mud, it seems not to end. The creek cut about a 6 foot trench through the mud, above that is where the quickest sinking is. Any advice to sinking in this kind of mud