This is a grip for the GoPro.

It can be operated with one hand or with 2 hands, providing a much more fluid and static film operation.
The whole setup can be used on land, but also for diving, but actually this design has been optimized for ScubaDiving.

For a clean buoyancy of the camera, please print with enough infill (i.e. little air inclusions).

In bright colors you can see the thing well and you can attach it with a cord and a carabiner to your buoyancy vest.
The whole part is sized so that it still fits into the pockets of the buoyancy vest.
So you can comfortably put the cam in the pocket, dive from the boat into the water, swim to the dive site and then take the camera out.

Please do not forget to rinse the whole camera with fresh water after the dive.
This also applies to this handle.

Have fun on your next dive and let me know how it went with filming.