Paradise on earth! A must visit,The Spice Island lies about 1hr by plane, on the coast of Tanzania. Or if you take a 12-13hr bus ride to Dar es Salaam you will be able to take a ferry to Zanzibar.
Though the bus gives you the chance to see the rural Tanzania, it is a really long and rather expensive way to get to Zanzibar. This is because you will have to overnight in Dar es Salaam the take the ferry the next day, hence spend more. There is a enough airlines which fly directly to Zanzibar and you will have more time to explore this beautiful Island, go on excursions, dive if you can and enjoy the snow white uncrowded beaches.