How to take video of the inside of a cave, from above, with an action camera?

I am interested in lowering a Go Pro Hero 7 into a cave: to record video and to take measurements with two scientific instruments, and want to ask your advice on what would hold the camera.

Specifically, I want to lower in two instruments: light meter (how much light); air particle meter (how clean the air is).

I estimate the cave would be about 15 feet to 30 feet deep (about 5 to 10 meters). I can lower lanterns in, on ropes, for light. It’s unlikely that I would go into the cave myself. Instead I would prefer to stay above on terra firma!

I would appreciate your suggestions.