The waters around Mafia Island host an outstanding mosaic of tropical marine habitats with coral reefs, sea grass beds, mangroves, and inter-tidal flats. In addition, a remnant block of threatened lowland coastal forest survives along the eastern seaboard of the island. The area has been recognised internationally as a critical site for biodiversity. It has national importance as one of the few remaining reef complexes within Tanzania's coastal waters, relatively intact and the productive fisheries and other marine resources provide food and income for the local community. 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.
Most of the marine area of the park is less than 20 metres below mean tide levels. This area includes much of Chole Bay, the extensive area south of the bay enclosed by Mafia Island, Jibondo and Juani islands and several reef areas south of Bwejuu. Extensive inter-tidal flats stretch along the southern part of Mafia Island, around Chole and Juani islands and between Jibondo Island and Kitutia Reef. A channel of 20 to 30 metres in depth carries tidal water through Kinasi Pass and Chole Bay as far as the Chole channel. The waters on the southwester side of the marine park, especially those west of Kitutia reach a depth of 40 metres. The flow of the main current into and through the marine park area is interrupted by the islets and reefs, and is also strongly influenced by diurnal tidal currents generated by a tidal range of up to 4 metres. This results in a complex and multi-directional current system. The tidal range in the marine park is consistently large during the year. The mean spring-tide range is 3.3 metres with a maximum of 4 metres. This neap-tide range is approximately 1.5 metres. The sheltered western side of Mafia Island is heavily influenced by sedimentary material discharged from the mainland. What direct influence the Rufiji Delta, facing Mafia, has on this is unclear. The visible sediment plume emanating from the delta appears mostly to be carried northwards by the prevailing East African current before it reaches Mafia's west coast even after heavy rains.
The eastern side of Mafia is exposed to the full force of the Indian Ocean and a 33 km outer fringing reef stretches along of the full length of the eastern seaboard and encompasses Mafia, Jibondo and Juani Islands with Kitutia Reef lying at the southernmost point. Chole Bay, a large enclosed body of water, floods and drains twice every day through Kinasi Pass. The main inner section of Kinasi Pass, together with the sheltered area south of the pass, has a highly diverse topographic structure and hydrology, and the highest diversity of hard coral and other reef species is found in this area. Other sheltered sub-tidal areas going west from Chole and Juani Islands across to Mange Reef and Bwejuu Island, are less species rich, characterised by shallow algae and coralline reef platforms and sandy areas studded with coral bommies. There are also significant patches of sea grass in these areas especially to the western side.
The Dar-es-Salaam Marine Reserves (DMR) comprises of Bongoyo Island Marine Reserve, Mbudya Island Marine Reserve, Pangavini Marine Reserve and Fungu Yasini Marine Reserve. The Minister of Natural Resources and Tourism gazetted these islands in June 1975 after it was found that the reserves had abundant resources that were in need of protection. The reserves system has a total area of 15km2, with Mbudya Island Marine Reserve being the largest and Funguyasini Island, the smallest. The Dar es Salaam marine reserves system are unique due to their proximity to Dar es Salaam city, potential biodiversity and richness, good scenic diving and snorkelling sites; ideal refugee for marine birds and good sites for Dolphin viewing. Occasionally whales have been spotted (Humpback whale) on the deep waters around the reserves during the months of May to August.
The island part of the reserve occupies an area of about 0.63 km2, narrowest in the southeast and broadens gradually in the northwest. The island is built upon rugged coral rocks with scattered sinkholes. The raised sandy beach is more pronounced to the northwest providing good swimming beach and anchoring facilities for the small boats (tourism activities). The reef around the island is very shallow and access is difficult at low water except at the main sandy beach, which is used as mooring and landing site for both the Slipways boat charter and other visitors. The intertidal zone surrounding the island comprises small sandy beaches as well as coral based rocky flats. The average tidal range is approximately 3m, with large spring tides attaining a slightly larger range. The underwater habitat range from shallow gently sloping coral reefs, sandy expanses and sea grass beds.
The island offers fabulous snorkelling and diving opportunities and is a favourable day outing for visitors to the section of Tanzanian coast. Mbudya Island is situated about 3 km offshore, within easy reach of the hotels on the North coast of Dar es Salaam.
There are nearby sand beaches on the western and eastern sides. On the western side, it is possible to have barbecued fish with chips and drinks. There is plenty of shade under the Casuarina trees.
Maziwe Island is located in the Indian Ocean at a distance of about 15 nautical miles east of Pangani town. This submerged island that at one time had forest cover extending for about 10km. The main island species found by then were huge trees like Casuarina cunninghamiana (Mivinje Bahari) Breonadia salicina (Mgwina), Cocos nucifera (coconut plantations) fruit trees and other shrubs including tall trees. Maziwe remains an ideal place for swimming, snorkelling and diving as well as research expedition, sunbathing and watching dazzling tropical fish. There are wide ranges of marine species diversity within the Maziwe Island Marine Reserve. Over 200 species of fish, 35 Genera of corals (soft and hard), number of sea-grasses, many types of birds, different algae and sponges are also found in and around the Island Reserves.
Mnemba Island is a coral atoll in the Zanzibar Archipelago, surrounded by thriving, vibrant reefs and gin-clear Indian Ocean. Welcome to some of the best diving in the world. The waters around the island are awash with colourful marine life - with approximately 4 times the range of fish species than the Caribbean. With an average visibility of between 20-60 metres and warm waters, (average temp 27 degrees C), and numerous colourful shallow sites to explore, it is a stunning diving location for experts and beginners alike. Visibility is generally better after the November rains, between November and March. Mnemba's 'house' reef is one of the best in Zanzibar, with clear shallow waters, and drops to an average of 40m. The Great Wall is stunning, plunging steeply from 35m to 70m. Dolphins and turtles are commonly seen on dives here.
