Although I am not likely to use 8K video underwater (4k60 maybe), I wonder about the heating issue when in an underwater housing that is a partial vacuum (I generally pump out about 6-7bar). The water is generally coldish but with no thermal air to conduct... Will be interesting to try. Even if we get to that thermal point, can we still use it for stills?
Interesting point! I'm curious about this as well and hope that you share here, at CR, your experiences, whenever possible.