Far quieter than Zanzibar, Mafia Island is a marine park first and a beach destination second — a low-key, laid-back alternative for travelers who want the coast without the crowds.
Its coral reefs are protected within the Mafia Island Marine Park and rank among the healthiest in East Africa, drawing serious divers and snorkelers.
The island's biggest claim to fame is its resident population of whale sharks, the world's largest fish, which gather to feed in Mafia's plankton-rich waters and can be snorkeled with on a boat excursion.
October to March is peak whale shark season, though the diving is good for much of the year.