That is scary. I have been stuck past my waist, but was lucky to have buddies with me who laughed and cheered me on. Good thing he wasn't in a tidal marsh.
Keeping yourself in good physical shape and knowing you limitations is an important part too. Had a friend a few years ago go out on a solo hunt. Decided to try and wade in a mud creek and sank up to stomach. He was about 300lbs and couldn?t pull himself back into the boat. Had to get rescued.