Mnemba Island, off Zanzibar northeast coast
A tiny triangle of white sand barely half a kilometre across, Mnemba Island sits inside one of the richest coral reefs in the Zanzibar Archipelago. The surrounding Marine Conservation Area protects a reef so biodiverse that divers travel from across the world just to slip into its waters. The island itself is private, reserved for guests of its exclusive lodge, but the reef that encircles it is open to snorkelers and divers on day trips from Matemwe and the north coast, with regular dolphin sightings and, in season, passing whales.