Mafia Island Marine Park is an excellent world-class diving destination with the richest reefs in the world. The park covers the Southern part of Mafia Island and includes the inhabited islands of Chole, Juani Jibondo, and Bwejuu. Also, several uninhabited islets and the associated waters.

Mafia Island marine park and its chain of small islets lie approximately 120 km south of Dar es Salaam. Also, 20 km offshore from the eastern extent of the Rufiji. Therefore, this is one of the largest delta systems in Africa. So, to the east of Mafia Island in 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.

The marine park area at Mafia Island extends across some 822km2, more than 75% of it below the high watermark. The area hosts an outstanding mosaic of tropical marine habitats including coral reefs, seagrass beds, mangroves, and inter-tidal flats. In addition, a remnant block of threatened lowland coastal forest survives along the eastern seaboard of the island.