Outside of the broads it's actually quite normal for people to take to the soft mud for a number of reasons. Including; doing repairs/maintenance to stern drives (You put a flat board on the mud and you can walk on it without sinking - Not that I recommend trying though) (even antifouling and changing seacocks), to doing a bit of sunbathing and even getting a nice nights sleep. I guess it's probably discouraged on breydon because it's a RSPB nature reserve (and seems that everyone panics), so although these hirers have clearly messed up the other picture floating around of a private craft could just be relaxing.. . Breydon is a lovely spot and I would love to spend a couple of hours laid back enjoying it, instead of rushing through... (one day lol ).