Report 27261: Couple witness rocks thrown and possible vocalizations between two animals on either side of a fishing dock near Williamsville

My wife and I were night fishing off the docks of chaonia landing at lake wappapello in late fall early winter 2007. At around midnight we heard rocks being thrown into the lake from across the bank.  we went to the end of the dock to see what was going on. coming down the bank along the waters edge rocks were being thrown into the water about every 50 feet or so, big rock the size of bowling balls. the bank I'm speaking of is actually an island with water on three sides of it for about 5-6 miles, and it ends right in front of the boat docks we were fishing. coming straight towards us along the bank something was throwing these boulders into the water, when out of the trees came a rock straight at us and landed in the water 6 feet in front of us followed by a very deep growl and grunt.  the distance from the end of the dock and the opposite bank is maybe 50 feet. we stood there looking into the trees desperately trying to see whatever was growling at us yet it stayed just inside the tree line.  the lights from the docks light up the whole opposite bank from point to point.  up and down the bank this creature went tossing rocks and growling and screaming.  then we noticed another creature on our side of the bank coming down towards us throwing rocks into the water howling after each rock hit the water.  the two were doing this in unison up and down the bank for over an hour while we were trapped on the dock in fear.  the one caught on the island worked his way into a huge angry fit. the two seemed to be letting the other one know where the other was.  there is so much we witnessed, heard saw that i cant possibly write all down here. for nearly two hours we stood terrified as we realized what we were experiencing. we have not really told our story to any other than family. its too unbelievable.