Ok, I see now what you are doing now. I have 2 sets of rear lights. I ran my wires tucked up into the frame area and ran them into the cab and tied in to the fuze block. I have a rocker switch to turn the 100 watt lights off and on. I have been in some 3 1/2 ft water and never had any issues. Are you planning on going really deep in water?
Here is my 100 watt 'Bling' rear lights mounted under the bumper and 50 watt lights mounted on the bumper (amber lens). Got them on Ebay years back. Good lights for really dark places. The amber lights are remote controlled. I can turn them on with the remote when we are out in the dark hiking and see where the truck is from about 75 ft away. The lights help light up the background when you are out in the wilderness camping or boating and need to see behind you backing up when putting in the boat of taking it out.