https://www.ifoaming.com/products/interlocking-eva-foam-mat-under-pool/
Foam mats for under swimming pool consists of 8 pieces of comfortable and durable foam puzzle mat, which can be arranged under an above-ground pool to protect the basement from wear and tear caused by pebbly turf, pointy twigs, and other ground debris.
These foam tiles under pool are simply placed on the spot u plan to set up your pool. And these foam mats for under pool have been specially designed to lock together for extra stability and simple expansion. If 8 sheets of foam tiles for pool aren't enough to fit the size of your pool, you can combine extra packs and expand the area that the pool flooring covers.