Please indulge me in this brief rave about my new Nikon Z6 and pro lens...
I recently upgraded my rig from a very capable Olympus OMD EM 5 Mk II four-thirds mirrorless camera, M.Zuiko 12-40mm f/2.8 pro lens in a Nauticam housing with an acrylic port to the Nikon Z 6 full-frame sensor mirrorless camera, NIKKOR z 24-70mm f/2.8 S series lens in an Aquatica housing with 9.25" mineral glass dome port.
Returning home from my first dive trip with the new rig (Buddy Dive in Bonaire), I imported the images into Lightroom and carefully reviewed the details in my shots. I was completely blown away by the level of detail, clarity and sharpness I was able to get. As good as I thought the Olympus camera and lens were, it pales in comparison to the quality of the output I'm now able to achieve with my new Nikon camera an pro-level lens (AND glass port). I'm able to get about twice the number of usable shots with my new rig compared to my old one.
It's definitely not a cheap setup but if your budget supports it, I would definitely recommend taking a look at the Nikon Z6 with NIKKOR z 24-70mm f/2.8 S series lens*.
French angelfish with pin sharp eye:
1. Full size https://drive.google.com/file/d/1MPxXBNBt3AgMjP3HRHuOeI0ZhgjgM2NZ/view
2. Zoomed in https://drive.google.com/open?id=1609JwxyqVHPTfMiX3mjzfDQblaGaE0z8
Shot of my wife taken through 10 feet of water (clearly captures her eyelashes and pupils through her mask, the camera was focused on her eyes through a corrective lens which is why the parts of the image outside of her mask is not as sharp)
3/ Full size https://drive.google.com/file/d/1lwR57ZX1tQ_u7NL39hdNKcdrtRg1Sgur/view
4. Zoomed in https://drive.google.com/file/d/1FmB4h8wYoWssgpaIo3g7c0fyYE6qyp1p/view
(* No, I don't work for Nikon.)