The commercial whirlpools that we've encountered have the pump and control equipment in a compartment under/in the side of the tub and accessible ONLY with the use of a tool (suggest stainless or SOLID-brass fixings throughout). The equipment control cabling contained within this environment is gland-sealed against water ingress and, every interconnected item has TWO earth conducting paths; one the cable CPC, and an independent 2ndary earth conductor terminated on separate terminal/busbars. The compartments we've seen are closed at the top and sides to the extent of preventing jet-wash water from spraying in, but open at the bottom (below floor) to allow ventilation and 'contingency/breakdown' drainage BUT not open to human or pokey-finger access (eg: mesh-covered).
Take extra special care over the siting, choice and connecting of a control switch which must be waterproof. Be pragmatic I suggest, for even if a control switch is sited in a 'zone 3' 'don't try to be clever' this is specifically a switch that users ARE likely to attend when they are naked and completely wet including their feet and hands regardless of how many metres away you site it.
Look at the IEE Regs for details there is a special sub-section for whirlpools etc.
Only trying to help.
