Africa & Indian Ocean

Big encounters. What links the destinations in this region is less the beauty of the reef than the fact that they sit on migration routes: humpback whales, whale sharks and shark aggregations pass through these waters in particular months.

The calendar matters more here than anywhere else. Humpback whales move towards the equator in the southern hemisphere winter — roughly July to October — and pass along the coasts of Tanzania and Madagascar. Whale sharks feed around Mafia Island between October and February, and off Nosy Be between September and December. South Africa's sardine run falls in June and July. None of this is guaranteed; the season only raises the odds.

The second thing these places share is on land. Most of the tours in this region combine diving with safari, and on the islands with culture days — savannah in Kenya, Stone Town in Zanzibar, endemic nature in Madagascar. That is why the programmes are also open to companions who do not dive, and why they run longer than a pure diving trip.

The rainy seasons shift from country to country; each region's own calendar is written out separately on its page.