Good way to have a pool pop out of the ground. VERY expensive to fix.
I remember when they put in my gunite pool at my former house they told me the story of a pool that popped up out of the ground due to hydrostatic pressure. They advised me to never empty the pool entirely. I sold the house when the pool was about ten years old.
I was told that around year 15-20 it would need to be plastered again.