smee the tea colored water and foam/film on top of the water is the lake is turning over. The lake does this every winter time the cooler water on top sinks to the bottom of the lake and the warmer water on the bottom of the lake comes to the top causing the water to stir up and all the junk on the bottom comes to the top. But following the turn over the water will be the same temp from top to the bottom for the most part. I am sure there are people on here that can explain it more indepth.