Moorea

Diving here is boat-based, but only just. The centres sit on the lagoon along the north coast, boats leave from small docks, and the run out through a pass to the outer reef takes a few minutes, so a two-tank morning is back before lunch and leaves the afternoon for the island's bays, ridges and viewpoints. The shallow lagoon close to shore doubles as snorkelling and checkout ground, so groups that mix divers, learners and non-divers can work off one boat.

The fringing reef sits close in, so the underwater geography is compact: sand-and-coral shallows inside, a barrier reef broken by passes, and an outer slope stepping down to a drop-off. Sites differ mostly in how exposed they are. The sheltered slopes are calm, gently profiled dives over coral and sand; the pass mouths move water and are where the larger animals stage; and the outer edge picks up swell whenever the wind swings onto that side of the island.

Sicklefin lemon sharks are the animal the diving is organised around. They are habituated to divers, come in close and hold station over the sand and at the channel entrances, so encounters tend to be unhurried rather than fleeting. From August into October the humpbacks are around, and the season is felt on every boat: their song carries clearly underwater, and divers routinely hear whales they never see. In-water encounters are a separate licensed snorkel activity run under minimum-approach rules, not something added to a dive.

Moorea suits divers earlier in their diving than the Tuamotu atolls do. The lagoon sites are undemanding and the pass mouths are a manageable first taste of moving water, so a group of mixed experience can dive together all week, and it works equally well for anyone travelling with people who do not dive, since there is enough above water to fill the trip. Runoff and swell around the turn of the year close the exposed outer sites often enough that those months rate below the August-to-October stretch.