A Prison Island tour from Zanzibar involves a boat trip to Changuu Island (also called Prison Island), where you  can explore its historic prison ruins, interact with giant Aldabra tortoises at a conservation sanctuary, and enjoy swimming, sunbathing, and snorkeling in the beautiful surrounding waters. You have opportunities to see colorful peacocks, bats, and butterflies, making it a popular half-day excursion from Stone Town.