I am surprised that the technique of sitting on the back of a dinghy and pushing on the muddy bottom and propelling the dinghy across the mud is not more well known. As you push with the feet you just lift your bottom and the dinghy moves a couple of feet at a time. It works really well and you just end up with muddy wellies. You can get up to a respectable rate over the mud.
A similar technique but in which only an oar gets muddy is to stand at the rear of the dinghy (I am talking rigid here not inflatable) insert oar against transom so the blade is a bit under the boat and then, at the same moment, give a good heave on the oar and jump up so your weight is off the boat. With a bit of practice you can achieve good progress. Trick is to unweight at the right moment. Fail to do so and you either make no progress or break the oar.
Hilarious I would think ?
I have never tried that. Towing a dinghy through mud at Pin Mill with the boss sat in the back was a gruesomely muddy experience.