Mafia Island

Mafia lies about 120 km south of Zanzibar, at the mouth of the Rufiji Delta, and feels a generation behind the bigger island — a handful of small lodges, a single tarred road, and a pace set by the tide and the dhows. The Mafia Island Marine Park, gazetted in 1995 as Tanzania's first, protects Chole Bay and the outer reefs, where more than 400 fish species and 50 genera of coral live on walls and gardens that see a fraction of the divers of the Red Sea or the Maldives. Chole Bay's sheltered water is a good place to learn.

From roughly October to March, whale sharks gather to feed on plankton in the shallows off Kilindoni — close enough to shore that a snorkelling trip, not a dive, is all it takes to swim alongside them. Green turtles nest in Chole Bay, and the mangrove islands of Chole and Juani hold the overgrown ruins of a 19th-century Shirazi settlement. Mafia reaches by light aircraft from Dar es Salaam (about 30 minutes) or Zanzibar, and pairs naturally with a southern-circuit safari in Nyerere or Ruaha.