Swimming Pool Construction:
What are the stages of building a concrete pool?
The main stages of concrete pool construction:

Engraving and excavation. Based on a plan and section plan, the dimensions and depth of the pool at this stage are determined.
Then the metal mesh is laid.
Next are the hydraulic waits, the piping, the installation of the lights and branches, the perimeter networks (if the pool is overflowing) and hydraulic components which will be covered with concrete.
The formwork (moulds) is installed internally.

See the article here