Best setup for scientific fish UW photography

Hello everyone,

I am new to this forum. I'm an ichthyologist looking to upgrade my UW fish photography gear. I currently use a Canon G5 XII with a CMC-2 and an Inon D-200 strobe, which gives me a very versatile magnification range, but I'd like to switch to a mirrorless system with better autofocus, a larger sensor, and higher resolution.

My goal is to be able to photograph, during a single dive, a ~1 cm goby sitting on the sand, a moving damselfish swimming past at 0.5–1 m, and larger fish up to 0.8m in size. I don't do true wide-angle or aesthetic photography: I "just" want sharp photos where I can count the scales and fin rays. I would also like to keep the setup fairly compact for snorkeling, rough water entries, or when squeezing between rocks.

I have a generous budget, up to $15k.

After quite a bit of research, I'm considering several Sony options (I am open to other brands but they do not seem to offer what I am looking for), but none completely satisfies me:

• A6700: compact but APS-C, relatively small sensor, getting pretty old now (it pains me to put a lot of money into a model that will be replaced in 1 or 2 years), flash sync limited to 1/160s.

• A7C II: compact as well, but also getting a bit old, sync limited to 1/160s.

• A7CR : more pixels but sync limited to 1/160s, and also getting a bit old.

• A7R VI + 100mm macro + MFO-3 (+ possibly MFO-1 on double flip): lots of resolution for cropping, excellent AF, the MFO-3 would allow a wider field of view for larger/closer fish. But the whole setup seems bulky.

• A7R VI + 28–60mm + CMC-2 on a flip adapter (+ MFO-1 if useful?): this option would better replicate the philosophy of my G5 X II: versatile, more  compact and lighter than 100mm+MFO-3, but I'm afraid of losing a lot of working distance, magnification, and perhaps ease of focusing on very small fish.

My ideal lens would probably be a small macro zoom, for instance something like a 40–100mm capable of going from infinity to 1:1, but that doesn't seem to exist. Failing that, a compact 50–60mm macro with extremely fast autofocus might be the best compromise, but the Sony one gets bad reviews.

I would appreaciate any advice.

My best

Fred.