Very cool! I have been wanting to build one. Did you find plans online or do you have plans you are willing to share? Can't wait to see some videos!
I searched online using diy trollpro as my starting point. It's made out of 2" PVC fittings. All of the hardware is stainless steel.
The parts list:
1-2" end cap.
2-2" unions.
1-4" x 2" reducer.
6" 2" PVC
1 large tear drop zinc.
1-1/4'" eye bolt, washer, lock washer and nut.
1-1" 1/4" x 20 washer, lock washer and nut for tripod mount.
1-Gopro tripod mount.
1 pool noodle for flotation.
I also ran a short piece of 250lb test power pro inside from the towing eye bolt to the back of the Gopro and attached it with a heavy duty swivel.