On our return to shore, we anchored off the coral reef and I spent a magical hour gazing down through the crystal-clear water at waving seagrass, coral mounds and a mass of brightly coloured fish that looked as though they had come out of a tropical aquarium. Zanzibar may not have the biological diversity of, say, Madagascar, with its variegated population of lemurs and other mammals, but if you are interested in primates, as I am, a visit to the Jozani Forest Reserve is truly rewarding. The reserve is located in the central east region of Zanzibar island and is home to the rare red colobus monkey, which is native to Zanzibar. These monkeys are full of character, and roam freely. Jozani has an excellent nature trail and the guides are both well trained and informative. The reserve runs right down to the sea, ending in a mangrove forest (a duckboard walkway helps visitors negotiate the swamps). The disappearance of mangrove forests around the world is one of the great environmental challenges of our time and Zanzibar's efforts to conserve its remaining wilderness is one of this wonderful island's many unsung stories.