I was fortunate enough to go on a one day island tour from Nadi in Fiji. I chose the sailboat tour that took us on a high-speed catamaran from Nadi to Mana Island, then we boarded a large schooner and travelled around some of the smaller islands.
I was lucky that day, supposedly it was raining at the hotel all day, but we only had a few patches of cloud just after lunch.
We also got to do a bit of snorkeling off of this island, and there were coral reefs about three feet from the shore. The water was a bit rough and the tide was strong, so it took a bit of effort just to stay in one spot. But the coral and the fish were gorgeous. And I almost found Nemo.