Savai'i & Upolu

Diving fits around the weather rather than a timetable. Sites sit just outside the fringing reef, often only minutes from the launch point, so a two-tank morning is the standard shape of the day and afternoons go to the land side. The south-east trades leave the north coasts in the lee more often than not, and operators move around the islands rather than cancelling, which is the main reason a week here holds together.

The rock is young volcanic and barely weathered, and that gives the sites their shape. On Savai'i the flows are recent enough to date: Mount Matavanu erupted from 1905 to 1911 and ran lava into the sea on the north coast. Underwater the result is tubes, arches, chimneys and boulder fields, so a dive is often a route through structure rather than a swim along a reef. Visibility is decent but variable, because rain off these steep islands puts runoff straight into the water.

Shore diving is a real option here rather than a fallback, and the sheltered lagoon sites stay usable when swell closes the outside out, which is what keeps a trip going through a rough spell. The outer edge is a different proposition: the shelf is narrow, and where it ends there is surge and moving water. It suits divers touring both islands by road who want dives fitted around lava fields, waterfalls and villages, and who prefer topography and small animals to a big-animal count. Book ahead, because capacity is thin and one boat out of service can leave you without diving.