The main island of Mafia is about 48 km long and 17 km wide at its widest point. The 20 kilometres (12 mi) wide stretch of water between the delta and the island is called the Mafia Channel. Mafia Island is part of a small archipelago with several much smaller islands, some of which are inhabited. The main town on Mafia is Kilindoni on the west coast. On the east coast is Chole Bay, Mafia’s protected deep-water anchorage and original harbour. The bay is studded with islets, sandbanks, and beaches, and is protected from the east by reefs and Juani Island.
It is one of the largest delta systems in Africa. The southern portion of Mafia Island, including the inhabited islands of Bwejuu, Chole, and Juani Jibondo, and several uninhabited islets further west and south of the island, are also part of the park.
Mafia is a renowned great world-class diving destination with some of the richest reefs in the world. To the east of Mafia Island, tourists appreciate the warm waters of the Indian Ocean.