I _finally_ dove some reasonable number of dives with the 30mm, and am reasonably happy with the outcome. I did miss the 12mm wide end occasionally, but mostly the water was pretty clear so the extra working distance for fish portraits was not a big problem. This was a trip to San Salvador Bahamas and I was mainly taking pictures of macro stuff, where I appreciated the better autofocus of the 30mm vs the 12-50 with diopter.I use mine quite often with an AOI zoom ring. For better or worse most of the shots [1] from my most recent trip are take with the setup, with the lens in "normal" (as opposed to macro) mode. I do use a diopter (inon UCL-165) for some closeup stuff.
I have a 30mm macro that I keep intending to use more, but I don't really have the discipline to say "on this dive no turtle or shark photos"
[1]: Itza Resort, Belize, March 2022