The easiest way is going to be to drain the pond first. If you have access to a drag line, then greatl, but the mud you stirup with the dragline will kill the fish anyways. Once the pond is drained, let it dry out for a few days before starting work. Start at the shallow end and scoop the mud down to hard earth. My pond is on bedrock so once dug back down to bedrock, I can put a truck in the pond area to load and hual if I have to. I suspect somewhere the bottom of your pond should be pretty firm as well. I would open one single trench from shallow end to the drain, thru the middle of the pond before working toward each side. This will facilitate water drainage out of the rest of the muck. Expect water to build up as you dig, at least until you get your trench dug from one end to the other where the drain is. Might want to keep a check on grease in the wheel bearings if you get water levels that high.