The Youtube channel Backscatter has posted a glowing review of the Panasonic Lumix GH5 for underwater shooting. The camera is a favorite of low budget film makers and those looking for the utmost quality with 10 bit color in a small package. The Backscatter review also points out that the slow motion feature of up to 180fps in Full HD works really well underwater.
We, however, recommend you stay at 120fps full HD to avoid some artifacts like moire and aliasing which the at 180fps show up easily and at 150fps are there to a lower degree. The GH5 can white-balance under water and does a stellar job at different depths according to the review.