Japan in December Diving recommendations

Hello all!

I have an opportunity spend December in Japan and as I have my dive gear with me, naturally the first thought is where to dive.

Recommendations for nice dive spots with 15+ Celsius temperatures (while I am fine with cold, the wetsuit has it's limits and as a big, clunky Nordic, not optimistic about rentals) which are suitable for decently experienced diver (mostly in cold, dark and murky waters).

Preference for dive centres on more dive club-style (and if with B&B or dorm, even better) over resorts with valet services type of places (I have always set my gear and it causes some confusion and awkwardness if that is not normal in the dive centre procedures). Also if tec diving courses are offered, it is definitely a plus.

Looking forward to hear from you people and mean while if you are diving in Korea, feel free to message me!