I have always set my 7DII at +2/3 stop EC. If I shoot as metered, I get underexposure.
That roughly ties in with what I was seeing. The underexpose isn't really noticeable until the iso starts to go up. I would have said the water and it's myriad reflections would not have helped, but not all the shots had water in them and my 7DI didn't seem to exhibit the same trait. I will see if I can get an image off a server somewhere, but I'm not at home at the moment (were the files are) and I think the consensus would be simply that it was underexposed (I reckon I pushed around 1 stop in LR). I did check that I hadn't nudged the exposure, or something similar and I with Av and fixed iso so I don't see the problem being there. I use LR6 for conversion btw
I do love the shutter sound on the 7DII. Sounds really well damped, I assume this is the motor powering the mirror up and down and not having a spring return?
So if I over expose by around 2/3 of a stop do I run out of headroom and permanently blow out the image with the 7DII, or will it still be recoverable? I can see this will help noise as a side product