Replacing the Pool Liner: Day 7
By the end of the 27th, the new, very snazzy looking liner was installed and we were beginning to fill it with water.

You can see a weird air-pump device inserted under part of the liner to hold it to the side. The reason you don't want an empty vynil-lined pool is that without water pressure (or in this case suction) pressing it to the sides, it'll deform.
Their lawyers have probably insisted that they install the following sign:
You have been warned!