Well, that is at least a pretty place to live.

All I know about Hawaii is that ya can't have more than 10 rounder mags there. Someone else can fill in more for ya...

Yes, all firearms must be registered in Hawaii within 72 hours of arrival.

Concealed weapons permits are "may issue" in theory, in actual practice, they are non-existant.

Open carry is prohibited in public areas.

Handguns may not be possessed without an approval permit from the police.

Good luck!

I lived on Oahu (Scholfield Barracks (Army)) for five years (my oldest daughter was born at Tripler Army hospital). It is a VERY liberal (politically) state. It is a very beautiful state and if you love the water, which I assume you do since you’re submerged under it for extended lengths of time, then it’s fun. Good scuba/snorkeling. Just watch out for the big waves on the North shore in the winter. One about took my kids away.

I did not investigate the CCW issue when I was there and it was in the early nineties anyway.