Underbody lights that use a relay to trigger from the interior lights. Has completed video along with build info.

Here is the parts list that matches what you will see in the video:
Underbody LED lights rated for underwater use https://www.amazon.com/gp/product/B00...

Marine Adhesive for gluing the lights in place https://www.amazon.com/gp/product/B00...

Clips to help hold the LED strip lights in place (you will need to replace the included screws, they are softer than lead) https://www.amazon.com/gp/product/B0B...

Wire for connecting LED light strips to the relay under the hood https://www.amazon.com/gp/product/B00...

Adhesive lined heat shrink tubing for the LED light wires, use after soldering https://www.amazon.com/gp/product/B08...

Relay power wire to connect to battery, with fuse (cut off the cigarette lighter adapter) https://www.amazon.com/gp/product/B0B...

Solid State Relay to use the power to the interior lights as a trigger for the underbody lights. First tried a traditional electro-mechanical relay, but it over loaded the factory interior light system (there was an unhappy buzzing from one of the control modules). https://www.amazon.com/gp/product/B09...

Quick connect wire taps for connecting the LED light wires to the larger relay wire underhood. https://www.amazon.com/gp/product/B01...

Cover these connections with Waterproof Liquid Electrical Tape. https://www.amazon.com/Gardner-Bender...