I am a Nauticam NA-XT3 / Fujifilm X-T3 user and, as ChrisRoss said, I am very happy with the combo. If Nauticam keeps making housings for the XT series (ie XT-5), I will go for one, not just because I have built a system for macro (fujinon 80mm macro) and wide angle (fujifilm 15-45 + MWL-1), but also because I like it. It meets my expectations, I love the XT series cameras, and Nauticam build and excellent housing for the X-T3. I have to admit that I mostly shoot macro (you can see some of my pics on my instagram account @wetdereamsphoto) but I see many options too for wide angle in the Nauticam port charts.
I understant that there are better options for uw photography than Fujifilm, but for me, as a novice uw photographer, it is more than enough.
Best Regards.