Most people know that Zanzibar is an island, but few know it’s actually two islands. Unguja gets attention for its bustling Stone Town, spice plantation tours, and chic hotels, but lesser known Pemba Island delivers the real adventure. Thirty deepwater miles north of Unguja, Pemba supplies most ofthe world with cloves, harbors some of the top dive sites on the planet, and remains a stronghold of Swahili culture, with mentions of it dating back to the journals of ancient Greco-Roman explorers. Fundu Lagoon, an 18-bungalow retreat on Pemba’s southwest side, is one of only a handful of lodgings here ($370, including meals; fundulagoon.com). At nearby Manta Point, schools of giant rays (some the size of Mini Coopers) rise from blue depths; in the fishing villages, Swahili craftsmen hand-make wooden dhows as they’ve done since the days of Sinbad. Visitors to Pemba are few, and residents regard the arrival of outsiders as a welcome diversion. An invitation to sail with the locals should be considered a privilege: The Swahili are some of the last indigenous African seafarers.