Stunning Mnemba Island lies roughly three miles off the northeastern tip of the main island in Tanzania's Zanzibar archipelago, cast out in the Indian Ocean like a shimmering string of jewels. The five-acre, triangular wedge of an island takes only half an hour to circumnavigate on foot, but this short walk gives a good sense of the area's distinct and diverse habitats, home to a mind-boggling array of exotic Indian Ocean wildlife. Mnemba is capped with pine trees and ringed by white sand that's the toe-sinking consistency of flour. On one side of the island, waves crash like a soothing metronome; on the other, a snorkelers' garden lies just offshore in tranquil, cerulean waters.

The entire island, including the resort, is owned by &Beyond (recently renamed from CC Africa), an ecotourism outfit that invests in conservation and community empowerment. Mnemba's only inhabitants are staff and guests. And with only ten seaside bandas, or cottages, exclusivity is assured.

Stunning Mnemba Island lies roughly three miles off the northeastern tip of the main island in Tanzania's Zanzibar archipelago, cast out in the Indian Ocean like a shimmering string of jewels. The five-acre, triangular wedge of an island takes only half an hour to circumnavigate on foot, but this short walk gives a good sense of the area's distinct and diverse habitats, home to a mind-boggling array of exotic Indian Ocean wildlife. Mnemba is capped with pine trees and ringed by white sand that's the toe-sinking consistency of flour. On one side of the island, waves crash like a soothing metronome; on the other, a snorkelers' garden lies just offshore in tranquil, cerulean waters.

The entire island, including the resort, is owned by &Beyond (recently renamed from CC Africa), an ecotourism outfit that invests in conservation and community empowerment. Mnemba's only inhabitants are staff and guests. And with only ten seaside bandas, or cottages, exclusivity is assured. The island-luxe huts were hand-built mainly by weaving together traditional Zanzibari palm matting. They're set back from the water and tucked into the shady edge of the forest. Each one is built on a platform over the sand and has a giant private veranda with perfect ocean panoramas and serious napping potential. The work of skilled local artisans—like the intricate woodcarving for which Zanzibar is famous—is foremost in the spacious, split-level cottages. Living areas are cushioned and comfortable, and the oversized beds are covered by a canopy of soft muslin.

The common areas of the resort are anything but. The elegant, sweeping arc of the wall-less, thatched-roofed bar and dining areas opens to the wide expanse of white sand and coral outcroppings. Say the word and dinner will be served al fresco at tables closer to the shore, so close to the surf in fact that tepid water laps at diners' feet. Guests feast on fresh fruit and vegetables and on East African delicacies made from fresh fish and shellfish that arrive daily by ngalawa, a traditional wooden dugout.

When islanders tire of relaxation and pampering, adventure begins just footsteps from their bandas. There's a lot to be discovered on a trek to Mnemba's interior. With no predators, baby Aders' Duiker and the rare suni antelope flourish here and can often be seen snacking on Dune Cross-berry branches. The purple-banded sunbird and iridescent paradise flycatcher can be seen flitting around a forest filled with whistling and screw pine, wild rubber, and giant-leaved fig and coast milkwood trees. The edges of the forest are also the chosen nesting spot for the threatened green turtle, which can be seen laying eggs here from December to March. (In 2008, 106 healthy turtles hatched and waddled down to the sea.)

Since the island is surrounded by coral atolls that lie within a marine conservation area (which only resort guests are allowed to explore), Mnemba has some of the best diving in Zanzibar. The immediate area boasts over 300 species of fish that frequent the coral expanses, including the flashy tigerfish, cowfish, surgeonfish, and angelfish. Snorkelers are only a five-minute swim from some popular marine life viewing areas, and divers can choose from countless nearby spots like Poisonous Pinnacle, an outcropping of fire coral visited by leaf fish, stonefish, lionfish, and scorpion fish, to name a few. Mnemba's waters are also home to bottlenose, spinner, and striped dolphin and to the huge but harmless whale shark. Migrating humpback whales pass by Mnemba in September and October and thrill Zodiac riders by breaching and blasting warm seawater sky high. Windsurfing, scuba diving, and kayaking are other options.

A magical stay on Mnemba could only end with a sunset cruise on a traditional dhow, whose billowing white sails reflect a tangerine sky, or on a moonlight walk on the beach where the sand glows with phosphorescence in your footprints.

Heather Hansen is co-author of and has written for publications including Men's Journal, Outside, and Mother Jones.