Mnazi Bay - Ruvuma Estuary Marine Park (MBREMP) is in the Mtwara district of Southeast Tanzania and extends to the border with Mozambique. The area is considered to have globally significant marine biodiversity values and covers 650 square kilometres, of which 33% is on land. The park extends from the northern portion of the Ruvuma Estuary to Mnazi Bay, including the headland of Ras Msangamkuu.

The environment within the park includes mangroves, rocky and sandy shoreline, mudflats, salt pans, fringing coral reefs, lagoonal patch reef, seagrass beds, three islands (Namponda, Mongo and Kisiwa Kidogo) and numerous small rocky islets.

Surveys have found over 250 species of hard coral, 400 species of fish, and 100 species of echinoderms within the Park’s reefs. The marine and coastal plants and animals found within the Park are there because of the climate, the physical features, the influences of the Indian Ocean, and the overall integrity of the combination of habitat.

The Park is home to nesting grounds for Green and Hawksbill turtles, and a number of marine mammals have been seen in the area including migrating Humpback whales and the Indopacific Humpback dolphin. A large population of crab-plovers led to the area being designated as an Important Bird Area (IBA) in 2001.

The area was also once home to dugongs but the last confirmed sighting was in 1992, although there have been unconfirmed sightings since.

Close to 30,000 people live within the park, depending mainly on marine resources for their livelihoods; the park includes in its boundaries 11 villages and 8 sub-villages. There are few opportunities for development hence poverty is rife. This has created an over dependence on marine resources and the persistent use of destructive fishing methods.

Gas was discovered in Mnazi Bay in 1982, and wells were brought into operation in 2006. Gas from the wells is now piped to Mtwara where a gas to power plant provides electricity for the Mtwara and Lindi areas.