I'm assuming budget is loose since you're looking at Fiji and Bora Bora. There are many beautiful resorts in Bali. Many places around Bali (just not in the central coastal region) have nice marine life, but a lot of those corals you'll see may be dead unless you go further out). Most hotels on/near a beach can arrange water activities, whether it be offered by the hotel or through a third-party provider.

I'm against Aman because it's overpriced garbage but there are many FS properties to choose from. Also if you go see the sunset or overnight at Uluwatu (which I recommend you do), Alila Villas Uluwatu is a beautiful property.