You might want to consult with a geotechnical engineer. This is unlikely to be resolved by drilling a few holes in the bottom to try to sink it back down. It might go down a little, but probably not back to where it was. I would think that the following might need to be done:
1) Add well points to control the groundwater.
2) Redo all plumbing, including the light conduit.
3) Remove decking as needed and replace.
4) Cut out some of the bond beam and replace as needed.
5) Remove and reset all tile.
6) Epoxy inject cracks.
If you have a main drain, it is probably lost, and not worth fixing. The pool might have to end up being higher, which would mean replacing all decking to get the correct slope on the decking.
This kind of float puts a lot of stress on the transition from the deep end to the shallow end because the deep end is being pushed up and the shallow end is not. The pool might end up cracking across the transition line at some point.
You might be able to fill the pool while pumping out the groundwater to get it to go back down. However, I think that consulting an engineer is necessary in this case to get a professional evaluation.
How deep is the water table?
Is the contractor doing anything to manage the groundwater?