Yes that mud can be life threatening. When I was younger it happened and I always had a friend along to help me out. Now I am much older and my old hunting partners are mostly gone. three times this fall I got stuck while setting out decoys and had to get down on hands and knees to crawl out. This is no fun in freezing temps. I just got a pair of Mudders from Cabelas Waterfowlers catalog but since it is frozen up solid now I can not test them anymore this season. They are supposed to expand as you step in soft mud and I am looking forward to trying them next year as soon as the ice is out. They are listed on page 189 of the catalog.

I was in about a foot of water on a stream and sank up to my knees and was still sinking. I began to pull my feet out and crawled out on my knees. Got a little water inside my waders. After that I fished my decoys out with a fishing pole when hunting that spot.