How do you remove wrinkles from the bottom of an in-ground pool and why are they there if the pool is new?

Hydrostatic pressure or poor water chemistry. If the watertable is high the liner will float and when the water recedes will create a suction and pinch the liner. If your alkalinity and stabilizer levels are low the sanitizer will not have any molecules to attach to so it goes after the vinyl. The pulls the plastizer out the vinyl and causes it to prematurely fade and wrinkle.