Niue

There is no harbour, so the day starts with the boat being craned off the wharf at Alofi and lowered into open water, then lifted back out at the end of the morning. Runs along the coast are short, and site choice comes down to which side the wind is on, since there is nowhere sheltered to duck into. The island supports only a couple of boats, so trips are small and book out well ahead, and while sea tracks do lead down to the water, they are steep climbs better suited to snorkelling than to tanks.

The island is uplifted coral limestone, and the rock you dive is the same rock the road runs on, carried below the waterline and eroded from both sides. The reef edge sits close in and falls away into fissures and dark openings, so sites differ mostly by how far the overheads run and how much daylight follows you in. Some are open canyons with sand floors; others are short passages where the guide's torch does the work. A light touch and steady buoyancy matter far more here than depth or current.

Peak season reorganises the trip rather than just improving it: through Jul-Sep the same skippers and boats split their days between diving and time on the water with whales, so a week gets planned around weather and sightings instead of a fixed schedule. Dec-Mar falls inside the cyclone season and is the roughest, least reliable stretch of the year. It suits divers comfortable in an overhead who do not need heavy fish action, and who are happy with a quiet island, a hire car and an afternoon walk down to a chasm.