I have a small lake that I swim in. Over the last three weeks 3-4 times a week, previously about once every week or two through the summer months.
Its not very cold, but not like an indoor pool, probably about 60'F, or 16'C. I've come to really like it once I'm in and feel invigorated afterwards. I do about half hour, swim about 400m plus some kicking/arms only exercises and love all the wildlife I get to see.

~ Does anyone have an idea of calories used by exercising in cool water?

I seem to remember reading something about fat cells reacting to cold and 'releasing their energy' for use (ie. you at colder temperatures, you burn stored fat disproportionately more than just calories used doing the exercise)
~ does anyone use cold as a way to increase their fat loss?

I couldn't find an estimate for calories used, and to increase fat loss I just got bodybuilders advocating sitting in ice baths which is not really what I'm going for!