While the GH2 does suffer from a baked-in look where the curve does force gradations of color to band due to the limit of the 420 resolution, I think your issue is compounded by depth. With your clip, the problem is as you go deeper, the gradation of blues are broader than in the shallows like Berk's clips. That does make a big difference is how banding shows up. You'll have to try contain your scenes to keep the water column limited in range to avoid banding.
Thank you for the explanation, Drew. I was at 100ft when I took that footage so that makes sense. I will try shooting at different depths next time and see its effects.
Is this a common problem that plagues most/all video cameras when shooting underwater? What are your thoughts on using a GD filter underwater? Do you think this could help reduce such banding or is it simply the limitation of 420?
I appreciate your time and help.