mbtrade

I recently had a Viking pool and splash pool installed and the splash pool has a hollow sound underneath it like there is no base material under it. The splash pool is elevated with packed dirt around the outside and concrete poored on top. When the pool and splash pool were installed there was no gravel or sand put is as a base. The dirt was dug out and the pool placed diectly on the dirt and backfilled with the excavated dirt. It was just put in and I am wondering if it was installed incorectly. Any advice? Thanks