It is roughly triangular in shape, about 500 meters (1,640 ft) in diameter and about 1.5 kilometers (0.9 mi) in circumference. It is surrounded by an oval reef seven by four kilometers in extent. These reefs have been declared a Marine Conservation area. Mnemba Island and its reef are sometimes called Mnemba Atoll which is incorrect because an atoll is an island that encircles a lagoon, which is not the case for Mnemba Island.
Mnemba Island is a popular scuba diving site, with a wide variety of corals and associated species, as well as occasional sightings of larger species such as turtles and dolphins. Calm conditions are most frequent in November and March, with maximum visibility. Mnemba Island is a 90-minute drive from Stone Town across the main Zanzibar Island, before a twenty-minute boat crossing.
