Wondering exactly where that roaring lion is (Most game preserves in Tanzania): In any national park or concession with a relatively high lion population, your slumber will more than likely be disturbed by the distant but still powerful roar of a lion announcing jurisdiction over its kingdom. Reaching 115 decibels, the sound is carried across the plains 8km (5 miles) or more and remains one of the most powerful, thrilling sounds on Earth.
Watching a cheetah beat a Ferrari (Serengeti): The fastest animal on land, the cheetah can reach a top speed of 110km (68 miles) an hour; more impressively, it can reach this top speed from a stationary position in 3 seconds flat -- 0.2 seconds faster than a Formula 1 car! Despite occurring in vastly reduced numbers, your chances of seeing this critically endangered cat hunt in the Serengeti are probably higher than that of seeing a leopard stalk, as cheetahs are diurnal, preferring to hunt at sunrise and sunset, and usually on the open plains, where they can approach stragglers by running them down with a short burst of speed within a 400m (1,312 ft.) range.
Witnessing crocs snacking on easy pickings (Serengeti): The sight of thousands of animals plunging into waters infested with some of the biggest crocodiles in Africa is, for many, the eponymous moment of the "greatest wildlife spectacle on Earth." The Migration usually crosses the Grumeti River sometime during June or July (timing depends on rainfall during that particular year), while the Mara River can see continual crossings from June to September as the herds seek out fresh pastures on either side of the river.
Counting coins with a whale shark (Mafia Island): It's humbling swimming alongside the planet's biggest fish. Whale sharks weigh in at around 15 tons and can reach a length of 14m (46 ft.); the oldest is estimated to be 150 years old. While classified as a shark (not least because its huge mouth has around 3,000 teeth), these gentle giants -- their dappled skins giving rise to the Swahili name papa shillingi, which means "shark covered in shillings" -- are harmless and feed on enormous amounts of plankton sieved through their gills. Whale sharks tend to arrive in Mafia's waters around November and usually stay until February.
Being serenaded by a million wildebeest (Serengeti, Tanzania): East Africa's most abundant antelope is charmingly vocal at night, with a harmonious array of snorts and honks that sound not unlike a composition by Stockhausen, best appreciated when sleeping underneath the thin "walls" of a canvas tent. The Migration happens year-round, so find out where the herds are likely to be before deciding where to book; alternatively, time your visit for December/January, when some 1.5 million wildebeest descend on the short-grass plains near Lake Ndutu, birthing -- at their peak -- 8,000 calves daily.
Swimming with endorphins (Zanzibar, Pemba, and Mafia islands): Plunging into the waters above the coral reefs of Mnemba (Zanzibar), Misali (Pemba), and Mafia is a little like a good dose of shock therapy -- guaranteed to cauterize depression. Floating above this parallel universe, swarming with magnificently patterned and brightly colored fish, even the most committed skeptic cannot help but experience something like a religious awakening.
Tracking chimpanzees on the shores of Lake Tanganyika (Southern Tanzania): Gombe National Park, famed for the research undertaken there by Jane Goodall in the 1960s, vies with nearby Mahale Mountains National Park as Africa's best chimp-tracking destination. The hiking can be tough, but the reward -- touching base with a totally habituated community of man's closest relative in its forested home -- is utterly thrilling and engaging. If you're choosing between the two, the tracking is generally less demanding in Gombe, but Mahale is a wilder and more scenic location.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.