Unlike at Lake Victoria (the continent's largest by surface and, yes, the Nile's source), there are few large towns and industries discharging pollution. So the nearly mile-deep Tanganyika—which contains eighteen percent of the planet's freshwater, more than all five U.S. Great Lakes combined—remains one of the purest reservoirs on earth. The water temperature hovers at a tropical eighty degrees, and a handful of beaches and islets are the jumping-off point for divers and snorkelers to view more than two hundred species of fish, as colorful and varied as their saltwater cousins. Tanganyika also offers a unique safari-beach combo. My own plan is to observe the chimpanzees at Greystoke Mahale before heading south to Lupita Island, a clutch of luxury villas on a private island off the coast near the farm and fishing town of Kipili.

Alerted by radio, men emerge from the forest to meet the dhow at Kangwena Beach, dominated by a fantastical bat-wing building with a roof of soaring thatch. This is the dining hall and library of Greystoke Mahale, named after Edgar Rice Burrough's Tarzan character and founded two decades ago by an Irish bush pilot and former Sotheby's auctioneer, Roland Purcell. The lodge, which pioneered African chimp-watching safaris, has evolved from the original Arabian-sultan–style tents to seven thatched A-frame suites inspired by Central African bandas (the better to withstand sudden lake squalls).

Facing the beach from the tree line, my banda has a king-size wood-framed bed draped with mosquito netting, a veranda whose lounge chairs and table are made of recycled dhow beams, and an upstairs "chill out" platform reached by a ladder fashioned from a dugout canoe. Handwoven baskets and mats, blue appliquéd canvas from Cairo's tentmakers souk, and Tanzanian kanga cloth printed with Swahili sayings are utilized in a bohemian spirit and with a collector's eye. (Aphorisms are a Tanzanian tradition; my favorite, painted on an old dhow prow incorporated into the resort's sundowner bar, reads, "Myenyefina akosi sababu," or "Jealousy has no reason"—a pun and perfect summation of Othello.) The open-air shelter gently thrusts me into, rather than cossets me from, the environment. I am visited by wasps with golden bellies, black-and-iridescent-blue swallowtail butterflies, and a troop of vervet monkeys that know the customary 8 a.m. wake-up call signals a delivery of tea-tray cookies.

After unpacking, I kick off my shoes, put on a bathing suit, and head for the beach, bright-orange quartz pebbles and tiny glittering pink shells crunching between my toes. Gazing at the brilliant-green forest curtain while treading warm, clear water, I think those hotel developers have it right, that Lake Tanganyika could become Africa's freshwater beach paradise. But as soon as I set to sunbathing, a sharp jab from a tsetse fly ends my reverie.

These blood feeders—African conservation's greatest ally, because they stave off humans and domestic cattle with the threat of sleeping sickness—patrol the beach, smelling out bushbuck, blue duikers, and me. Their serrated mandibles can penetrate buffalo hide; a bite feels like being stuck with a safety pin. (Later that night, my tsetse bites will erupt into itchy welts; thankfully, sleeping sickness is rare and I'll return to sleep as soon as the hydrocortisone cream kicks in.)