I opened the files in CorelPaint XV. All of them appear to be 48bit files with 16-bits per color component. Due to restrictions of the tool I was not able to verify the effective amount of bits per channel. But the images do have a lot of latitude in color processing. You can actually adjust them into quite beautiful colors if you can accept the increase in the noise level. It would be interesting to calculate the S/N ratio with this exposure. My guestimate is 33-39 dB but I could be wrong.
What exposure settings did you use at this point of the video footage?
It would be interesting to view a fully color graded version of your video.
First, I really appreciate your effort into qualifying the images 
On the exposure, I believe on this dive my iris control got stuck and the iris was opened at the widest 4.5. On the same note, I am quite amazed by davinci resolve recovery from such over exposure issues. I've seen total white images come back a live. Like the sardine shot at the end of the clip.
Re. Viewing a fully graded version, do you mean a better graded one than the YouTube version? Can you elaborate more on this plz
It is important to recall that the BMCC is meant for film and the footage itself tends to be grainy, a desired affect for films, where I think it would not be desired for underwater. Still to be studied.
In the full version of Resolve there are various ways of reducing noise. I think the one that works on separate channels such as luminance may be effective.
Remember that I did the edit in resolve lite and that I am a beginner in color grading.