Vava'u

Almost everything leaves from Neiafu, and the boat spends most of the day inside the islands rather than crossing open sea. Skippers pick sites off the wind, and because the group's channels are so enclosed there is usually somewhere flat even when the outside is up. From July into October the same boats and crews are also running whale trips, so dive departures thin out and get built around them; divers coming in that window should book their tanks as deliberately as they book the whales.

The islands are limestone, and the rock does much the same thing underwater as above it: undercut cliffs, arches, chimneys and caves cut back into the walls, with coral growing on the ledges rather than forming a reef system of its own. Sites differ mostly by how much of that structure they carry. The channel dives are open and gentle, the pinnacles are compact enough to circle inside one dive, and the cave sites are as much about light and air space as about what lives in them.

Mariner's Cave is the one people talk about afterwards. The way in is under water with little daylight showing through, so you swim the tunnel more or less blind and surface inside a closed chamber where the air fogs and clears as the swell shifts the pressure; operators run it on snorkel as often as on scuba. Swallows' Cave is the opposite: big, open to the boat, and usually photographed from the inside looking out. Neither is technical, but both reward divers who stay calm in enclosed water.

Vava'u suits divers who want an easy week and are here for more than the diving. Depths are moderate, conditions are forgiving, and Neiafu is a working yacht base, so trips tend to mix diving with sailing, kayaking and time on the water rather than stacking four tanks a day. The Clan McWilliam, a steamer lost in the harbour, adds a wreck at the deeper end of otherwise shallow diving. Divers chasing dense coral reef or big pelagic action will find it quiet by Pacific standards.