You could use the option of a catenary (overhead) supply wire . See regs for height over walkways or vehicle access. Sometimes easier & cheaper than SWA (single wire armour) dependent on length & location & a lot less likely to pedestrian damage/or injury.
Hope this helps
Would you switch an electrical appliance on or off with your feet in water no matter how much you trusted an RCD? This seems a stupid place for an isolator!
Next room or as far away from the Zones as practicable.