If you used as much care wiring LV as you do in chapter 3 you shouldn't have as many trips. At 12v you need 10 times the fault conductivity to generate 5ma. (24,000 ohms @ 120v vs 2,400 @ 12v) I still doubt you could have those insulation piercing connections below grade that are common with the Malibu light but I doubt a few drops of water in a box would trip one.