We went to Fiji around 5 years ago for 10 days, on our way back from a gap year in NZ/Aus.
We were told if you want to see/experience the Fiji that you see on TV, in ads, etc, then you need to get off the main island and go to the smaller islands, which is what we did, and it was everything we could have imagined it would be. There’s regular boats that go to all the islands and transfers are super easy to arrange.
We spent around 8 days on these islands, but it is usually just the resort, surrounded by dense forest, so is very much a beach/pool holiday, which is exactly what we wanted after a year of solid working in NZ. We did heaps of snorkeling just off the beach which for us was absolutely incredible with heaps of fish and corals, but most places arrange scuba courses and trips too if that’s more your vibe.
Some of the islands are super pricey, but there’s quite a lot of more basic options which is what we opted for and they were perfectly fine with decent food.
LMK if you have any questions