Zanzibar is a short flight from the Serengeti, Nairobi or Dar es Salaam, which makes it the easiest beach to add to an East African safari. The island mixes Swahili history in Stone Town with long beaches, coral reefs and a relaxed pace that suits tired safari legs.
Choosing the coast is the key decision. The east coast, around Matemwe, Paje and Michamvi, has a huge tidal range, so the sea can retreat hundreds of metres at low tide. The north, at Nungwi and Kendwa, stays swimmable at all tides but is busier. Private islands such as Mnemba offer seclusion at a price.
The caveats: some beaches have seaweed at certain times of year, parts of the coast are developing fast, and Zanzibar is a malaria area.