I had originally thought of painted turtles but I have never seen any on the logs I have around, not that they aren't there. The first cages I made didn't have a top on them since I thought it was something small like a duck getting out there or a turtle. They got eaten right out of the cages. My next iteration had the top closed too. I was also worried turtles were swimming under the cage since the fence part went just below the water. When I closed off the top I extended the fencing all the way to the bottom. That worked but now the lilies are crowded in the cage.
The mud isn't to bad except in a few spots. I had the back dug out some when we built the pond last year but we didn't compact it any more than the track hoe driving around moving stuff around. Some of the mud is deep and I'll sink half a foot or so. The lilies are only in 1.5 foot or so of water so they don't have to go out that far. I put up a long fence today and took some pads out of the cages behind it to see if the deer will go around in 2.5 to 3ft water to get to the lilies. I also uncovered a couple and covered them with deer fencing instead using sticks to hold it about a foot above the water in a bigger circle. I left most of the lilies in cages while I see which works better. I moved my game camera closer to some I uncovered so hopefully it will catch them thinking about it or trying to get around. We'll see how clever they are.