The cavity did seem to have a bunch of water. What does that mean? Not something I've heard of before.
That is called "ascites" it is simply fluid that fills the cavity when the heart is bad and the kidneys do not get enough blood to work properly. If it is bad enough they will develop a sac of water/fluid under the skin between the legs or lower breast.
It does not hurt the meat, if you pick some up and notice a lot of them are "squishy" like fluid filled it is time to process as they will start dying off on you.
You need to withhold feed and move the water a long ways from the feed to force them to move when young. I only feed my CX's once a day for 15-20 minutes and make them free range the rest the day.] to prevent that.