Mafia is a large island lying off the southern coast of Tanzania, near to the Rufiji Delta. It is 30 miles from north to south, and up to ten miles in width. It is thus about half the size of Zanzibar Island to the north, and, like Zanzibar, is a raised portion of the continental shelf, not a coral island. The soil of Mafia is mostly sandy and the terrain very flat. There is a ridge forming a backbone to the northern end but at its highest point it does not exceed 200 feet above sea level. Along this ridge there is firm and fertile clay soil and cultivation of annual crops is possible. On the eastern shores there is some coral rock, making cultivation impossible.
Mafia Island and its chain of small islets lie approximately 120 km south of Dar es Salaam and 20 km offshore from the eastern extent of the Rufiji is one of the largest delta systems in Africa. To the east of Mafia Island is the Indian Ocean. Several smaller islands and islets are scattered to the west and south.
Mafia Island is the site of Tanzania's first Marine Park which was gazetted in 1995. The Park covers the southern half of the island and part of the north-east. Mafia is a real sleepy backwater ... unspoiled, un-commercialized and apparently timeless, where local people go about their traditional ways of life barely touched by the outside world. It is the ideal location for total relaxation in the sun, sand and sea, and a marine paradise for scuba and deep sea divers. The pristine coral reefs are spectacular offering a colourful undersea adventure experience, the world’s most unique underwater seascape.
Other activities on the island include bird watching, fishing and visits to local villages, historic archaeological sites, coastal forests, coconut plantations and traditional boat-building yards.