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. The main island of Mafia is about 48 km long and 17 km wide at its widest point. Several smaller islands and islets are scattered to the west and south.
Mafia Island Marine Park (MIMP) consists of eight small reserves along the Tanzanian coast under the Fisheries (Marine Reserves) Regulations of 1975, two of these are in what is now the Mafia Island Marine Park (MIMP), namely Chole Bay and Kitutia Reef.
The marine park area at Mafia Island extends across some 822km2, more than 75% of it below the high-water mark. The area hosts an outstanding mosaic of tropical marine habitats including coral reefs, seagrass beds, mangroves and inter-tidal flats.