I was interested to see if my Go Pro (well, local variant) could pick up footage underwater in the local fishing harbour. I really didn't expect much as visibility is commonly measured in poops. Anyway, it kinda worked.
This is v1. The bottom a-frame was to keep it steady and prevent spinning. The top had about 15 meters of twine that could be unfurled.
When it finally descended it floated just below the surface. Quickly modded it with a boulder and v2 was born.