South Pacific Island for Holiday/Snorkelling that you can fly direct to from Sydney?

[antarcticanewbies]

We are planning a round the world trip and will be in Sydney July/August and looking for a South Pacific Island to spend a few days. We are using oneworld so we would like to be able to fly direct from Sydney using Qantas or a oneworld affiliate such as Air Fiji. We would like to stay on a preferably quiet island where we can easily access the snorkelling (preferably without having to take a boat) and that offers other activities including walking/exploring. Any suggestions for an island and accommodation...

 

ps French Polynesia was on our list but not really doable with oneworld round the world