Kadavu & the Great Astrolabe Reef

Diving is organised around the lodges, each with its own boats and its own stretch of reef. The day is usually a two-tank morning out to the barrier, with the surface interval spent on a beach or in the boat, and something shallower closer to home in the afternoon. Rides are long and open, so trips get built around the tide at the passages and around the wind; a day that blows out is spent inside the lagoon rather than written off.

The reef offers three fairly distinct kinds of dive. Inside the lagoon are patch reefs and isolated bommies rising off sand in easy depth, calm enough to settle beside a cleaning station and wait. The cuts through the barrier are timed rather than simply chosen: the flooding tide pushes ocean water in and brings the clearer water with it, and slack is when a camera is any use. Outside, the barrier becomes an ocean-facing wall and slope, with hard coral gardens on the shallow shoulder and blue water off the edge.

April to October is the best of it, but those are also the months when the south-east trades blow hardest, so a guide's real job is picking which side of the island is in the lee. The water is at its coolest and clearest then. November to March is warmer, wetter and quieter above water, and it carries Fiji's cyclone risk, so days get cut short or lost outright. Lodges are small and largely self-contained, which makes nitrox, gear sizes and charging worth confirming before you book — there is no shore diving here and no second operator down the road.