I've always wanted to try the Canon 5D III with Magic Lantern underwater. In theory I felt shooting in raw would be more beneficial underwater than on land given the issues with accurate white balance and loss of light with every increment of depth. Unfortunately the post workflow is tedious and time consuming. I think once you get the hang of it, it will get faster and to me it was worth it.
Below were the results and my workflow in post.
Workflow:
Canon set to raw module and not MLV (need the speed of CF and not the sound)
Clips check and marked in/out thru MLV raw viewer
Lightroom/Capture one for correction and enhancements and exported 8-bit tiff
Compressor to convert to ProRes 422
FCPX for video editing
Motion for text
Compressor to convert for upload