there is a difference bettween 'grounding' and 'bonding'. A pool is required to be 'bonded' back to the pump motor (if it has one) only.
This then establishes a 'voltage gradient' in the pool, or in other words, the grade of any potential voltage will be the same ...
a tad hard to grasp at first, others will hopefully chime in.
Pools are addressed in art 680 of the NEC, pecifically 680.26 ( Bonding) would be good reading if you have access to an NEC
( National Electrical Code) at your local library.
here is one small part of 680.26
C) Common Bonding Grid. The parts specified in 680.26(B) shall be connected to a common bonding grid with a solid copper conductor, insulated, covered, or bare, not smaller than 8 AWG. Connection shall be made by exothermic welding or by pressure connectors or clamps that are labeled as being suitable for the purpose and are of stainless steel, brass, copper, or copper alloy. The common bonding grid shall be permitted to be any of the following:
hope this helps you