Question about water weight that comes off when fat comes off?

I've been thinking about the fact that here on r/loseit we talk about 1 lb of fat being 3500 calories, and that you've got to deficit that number of calories from your TDEE before you lose 1 lb (so for example, if I eat at a 500 cal deficit every day, I lose 1 lb per week).

My question is -- what about all of the supporting tissue needed to store the fat, especially the water? We are often told our bodies are "80% water" or some such. So, would that not mean that for every 1 lb of fat you burn, there should be additional water weight that comes off too?

My motivation for asking this question is that I've actually consistently been losing at a much greater rate than predicted from my diet, exercise, and TDEE. By about 2x faster. This was one possible explanation that came to mind. I'm not complaining, just curious about the science, if anyone knows anything about this.