Watch as a former accountant dives into his new career—clearing trash, dead creatures, and other potential blockages from the bowels of one of the most polluted cities on Earth.

Go beneath the surface with a pair of Antarctic divers and witness some of the world's oddest creatures: fish with "antifreeze," thousand-year-old sponges—perhaps even a new species.

Watch video and animated stills of an elephant massacre near Chad's Zakouma National Park—evidence of a major poaching problem along the park's borders. Warning: graphic content

Take a trip along three of Zambia's rivers—the Luangwa, the Kafue, and the Zambezi—home to spectacular sights such as the mighty Victoria Falls as well as national parks housing rare species.

Take a tour of the ancient city of Sanaa, which hums with merchants selling knives known as jambiyas—a business many believe may drive the rhinoceros into extinction.

Follow a day-by-day account of Katrina's wrath, from its birth in the Atlantic Ocean to the storm's costly aftermath. Warning: contains some graphic imagery

Go behind the scenes as conservationists release a captive-bred giant panda into China's bamboo-covered mountains for the first time.

Hear an Everest guide describe the rescue of an ailing climber who had been left for dead and was found hallucinating on a narrow ridge at 28,000 feet (8,534 meters).

Watch as a lone male bird tries to steal a meal from another family's turf and winds up locked with another male in a whirling dive bomb.

Take a trip down the Orinoco, and get an inside look at the diversity of life sustained by this vital and vibrant river.

Watch one of Alaska's famous rites of summer, as sockeye salmon face hungry bears and steep falls to mate in the upstream waters where they were born.

Join the world's fastest serpent—the deadly black mamba, whose venom can kill a human in just 15 minutes—as it zips through the African wilderness in search of its next meal.

Join three species of serpent as they outsmart enemies with deadly looks, clever camouflage, and even a "second head."

Watch as a king snake learns a painful lesson in the power of family ties when it tries to make a quick meal of a nest of thrasher chicks.

See how the Middle Eastern attraction had to rebuild after being swindled by some real snakes—false reptile experts who made poor enclosures that likely caused all but one of the park's animals to die.