Home inspectors often come across thermal pane windows with broken seals (this is when you see foggy type stains between the glass panes) but seldom see several inches of water in them. This window was around 30 years old. What you can not see is a crack above the picture line but the crack was on the interior. So the water was actually from condensation of the interior moisture. There was no vapor barrier in the basement crawlspace, and no cooking exhaust fan. These items contribute to the amount of water vapor available to condense on the outer glass pane, which then drips down and gets trapped between the two glass panes.