When laying the base of a swimming pool the pool company must use steel reinforced concrete to ensure it is strong enough to withstand any movement once the pool is finished. The base should be cast in one layer of concrete with the reinforcing grill mid way through the cement. It should not be cast in two layers with the grill dropped on top of the first layer once it had set! It should also have a waterproof membrane underneath which this hasn’t. Please check progress with your pool construction as even the big companies are not necessarily doing it correctly.
When building a pool it is very important to ensure that all pipework is properly protected from damage once the surrounding earth is replaced. Over the years, as the ground settles, unprotected pipes can easily become damaged. If your pool company takes a short cut then the repairs to broken pipes around your pool can be very costly and inconvenient to repair.