To quote Ronny Dahl, "The two most important pieces of recovery gear are a shovel and some Maxtrax's".
Our BobCat 763 skidsteer was up to its belly in wet sand, and pointed downhill. We dug out behind each tire and put a pair of Maxtrax (doubled up) under each tire.
Then I used the digging bucket to push the wheels up onto the treads, and backed right out.