No one will expect that!
Mud banks shift. I recently ran my boat aground on a mud bank only about 200 yards away from my mooring, where I had previously sailed quite safely before. The chart said I should have 2.5m at lowest tide, the draft of the boat is 2m and the tide was .5m, so a ridge of mud of about 1.0m had appeared since the last survey. Of course, if I had been watching the depth sounder, it would't have happened! I got the boat off by moving everyone to the side and lifting the keel out of the mud.