Mud and sand are the anti-Christ of sleds though!
It can be a little tough on sand, I find they slide really well over soft mud. Either way it beats carrying all those decoys. I used to fill my sled to the top with about 4 dozen decoys and then put a sack with another 4 dozen on top of it and bungee it down. Way easier to drag that across mud/sand especially when there is an inch or two of water than it is to carry it over your back along with gun and ammo.
When hunting open water, I used to put my ammo box in the first sled with loose decoys and sack and then tie a second sled to my ammo box and pull another 8 dozen behind it. Easy way to transport 16 dozen decoys across 1/4 mile of mudflat without wearing myself out.