Yes Auto WB works really well on the GH5 at depth. You more or less have to use that anyway if you are shooting with lights. I got some funny results when trying to manually WB with lights. That really only works if you can point the cam to something whitish on the wall/reef. I should maybe un-dust my Keldan blue filters and retry with them the next time. On ambient shots, the manual WB can get you closer than AWB, but then again, the difference is not huge and you can fix it in post if you're somewhat off. I must admit, I did not try tuning in the Kelvin numbers as an alternative route, just forgot...
The aperture was between 5.6 and 8. I moved it up and down a step as required, but its been in that region. ISO was on 400 most of the time, going up in 1/3 steps as required. The Panasonic 7-14 is not the fastest lens, but I think the results are ok, the "plastic" 6' Nauti-Dome was doing ok, but next time I think I'll use glass.
My impression is the GH5 codec holds up pretty well. I was worried that it might not be as good as the Sony, which is known to be very robust. The 400 Mbps should be even better, particularly in fast moving action.
The one thing I really did not like at all is the AF performance. Particularly with murky water and lots of particles floating around (which have been the standard conditions during this trip), its utterly useless. I deleted tons of clips for OoF. I hope the best for firmware 2.0.... I did take off my DNS Monitor after a couple of dives, because the drag was too big in those currents and manual focus on that tiny camera monitor at the lower end of the housing is a real pain.
On the bulls: We were behind a stone wall. Still, if that guy would have nicked his head he would have catched more than just my cam Not so much into this shark circus thing, but from time to time its fun.