First off I'd like to echo the sentiments of many people here with a huge thank you to the very knowledgable contributors on this site! Without you all, I would be at a complete loss as to how to maintain my pool, and I'm sure the photo below would not have been possible.
Perhaps this is 'ho, hum' to others, but I thought it was kind of interesting when I noticed the shadow of the cooler 70* water entering the warmer 95* water of the hot tub yesterday. The water depth is about 18" to the ledge where the shadow is and quite honestly I am very pleased with it's clarity! I will have to leave the 'hows and whys' this happens to those much more knowledgable than I, but I don't imagine it's too much different than heat waves coming off hot pavement. Never thought it would make a shadow however. I do have borates at 50ppm and that does some interesting things to the water........reminds me of the 70's in some ways.