Which Island chain would you recommend for intermediate Diving, Snorkeling, Food and Fishing?

Hi all,

I have 10 weeks in country and would like to devote one of those to an island chain.

Goals: 4 tank dives over two days at two sites. Can be same island.

Near-Daily Shore Snorkeling.

Whale watching tour available a bonus.

Shellfish harvesting/spearfishing tours a big bonus. Will be looking to book a sea fishing charter as well (dirt cheap, ideally I'd tag along with a local fisherman for the day. Ive had success in other port areas at dawn with a sign. If this is possible in Japan, recommendations appreciated 🙂 )

Strong preference for the presence of local culture (Not super into uninhabitied islands unless the fauna really justifies it). In my ideal world, I'd meet a local dive partner to explore with and I'd compensate generously. Also if there are any relevant regional cuisines, big bonus. ( I see Izu islands do a island style marinated sushi, things along those lines).

Looking for as budget friendly/ grunge backpackery as we can get. Not concerned about dive shop rep or safety. (I'm used to third world diving).

Thanks Folks 🙂