Tractor plunges headlong into giant mud pie... engulfed with blade still on dry land. Take heart, Neil, you know we'd all do exactly the same thing if given the chance. If I ever unstuck the thing, my next trick would be a faster running start next time.
Some smart-aleck will no doubt tell you to install turf tires, so you won't sink in so much.
Hope neither the tractor nor the boots are entombed permanently. If that stuff hardens, you'll need a jackhammer and dynamite to break them out!
Please keep us advised on the recovery effort.