Some of my first photos with A6300

I have very few lens choices for my Nikon.  Basically very wide, fisheye or macro.   No normal lens choices, which I miss.

Most of the time I shoot macro, because it's easier and there are lot of photo opportunities.

I started with 105mm macro (on FX camera).   For a dive I tried a 60mm macro, but it was simply too short.  I already feel like I am right on top of my subjects with 105.

So after one dive I quit using my 60 macro and its $400 macro port.

Looking for more focal length I added a 1.4 teleconverter (and $200 port extension) to give me an effect 150mm.   Now there is a focal length that works well for me underwater!

Unfortunately, the TC robs too much sharpness, so it's no better than shooting at 105mm and cropping.  Probably worse in fact.   And the TC slows down autofocus a lot, so it's better not to use it.

I am unclear what a diopter does.  Doe it allow for closer focus, or does it enlarge the image, or both?  I've only used a diopter (+2) when shooting my 16-35 wide angle.  I never noticed a difference as the corners seemed as bad with the diopter as without it.

That said, I have a much different experience with the Sea and Sea Internal Correction lens, added to my 16-35.   It really works well and makes the corners far superior to before.

My experience argues against a short macro, though your crop factor may make it a long macro compared to mine.