Up at Ft. Campbell we have a gravel quarry that is about 80 feet deep and crystal clear pretty muchdown to 60 feet then the water gets kinda dark the rest of the way. Anyway I would take my two man bubber raft out there and fish for Gills. While fishing I noticed a tree that had fallen in and was hung up on a rock face in 20 foot of water I think. The Gills would school up on this tree and swim circles above it. Coolest thing I ever saw. Wish I had an under water camera with me then, the water was so clear it looked like you could almost touch the fish but they were 20 feet down. all the rest of the fish would hug the wall as close as they could.