The group is devastated when two critical survivalists leave the challenge; with just 10 days left before extraction, Jeff is forced to change his survival strategy but a medical emergency quickly has him on the brink of a tap out.

A grueling five-mile hike into the snake-filled jungles of the Palawan island tests the three remaining teams of survivalists; the one-day journey turns into two days of chaos, and one survivalist must be medically evacuated from the challenge.

Medics closely monitor Jeff's high fever and prepare for his evacuation; the others scramble for a five-mile extraction journey through shark-infested waters; a survivalist pushes too hard leading to a medical emergency on the open sea.

A survivalist on a hunting expedition is bitten by a snake and requires an emergency medical evacuation; tensions arise between teams as hunting grounds get territorial; one group scores protein while their neighbors are on the brink of starvation.

Since the open sea is too dangerous to navigate, survivalists trek through a jungle filled with venomous centipedes, vipers and monitor lizards.

Ambushed by tropical storms, the survivalists are pounded by torrential rain and heavy surf; survivalists are stalked by sharks after taking to the open seas; one survivalist reaches his or her breaking point due to the storms and lack of food.

Desperate and depleted by their 60-day challenge, Jeff and Laura fish the South China Sea but are caught in a dangerous electrical storm on the open water; the brutal conditions on both land and sea lead to the Philippines claiming its first victim.

With resources dwindling, the survivalists venture into the shark-infested waters of the South China Sea searching for a much-needed meal; the all-female team is punished by scorching heat, brutal storms and a deadly insect.

Dropped into the South China Sea, 12 elite survivalists try to survive 40 days on land and sea; nearby, two all-star survivalists enter the same challenge looking to survive not just 40 days but an unprecedented 60 days.

XL All-Star Matt Wright seeks redemption as he takes on the brutal challenges of surviving Africa by himself; after more than 20 days alone, Matt begins a search for the other XL survivalists.

Dropped into the brutal South China Sea, 12 elite survivalists try to survive 40 days on land and sea; with resources dwindling, the survivalists venture into the shark-infested waters of the South China Sea searching for a much-needed meal.

The remaining survivalists struggle to regroup in time for a brutal two-day, 15-mile water extraction journey.

The survivalists' worlds collide with two other survivalists nearing the end of their challenge; the women fend for themselves while the men continue their unsuccessful mission to hunt wild pigs; a two-day storm strands two at an old camp.

Jeff is called out for his no hand-outs survival strategy but refuses to back down; a look at the survivalists and how they survived each other, featuring a free-wheeling discussion, interviews and never-before-seen footage.

Ambushed by violent tropical storms, the survivalists are pounded by rain and heavy surf; with the open sea too dangerous to navigate, the survivalists must trek inland; tensions rise between teams as hunting grounds get territorial.

Four weeks into the 40-day Amazon challenge, a violent two-day storm descends on the jungle.

Twelve elite survivalists enter an unprecedented 40-day XL challenge; in the Philippines, the survivalists must survive shark-infested waters before facing a dense jungle crawling with deadly snakes and monitor lizards.

Survivalists embark on several dangerous hunts to secure protein and prepare for their arduous extraction on the horizon.

The weak, divided group gets a much-needed victory when the hunters score a kill; to finish the challenge, the survivalists must complete a brutal extraction across deadly killing fields of lions, crocodiles and leopards.

Risking retaliation from a leopard, two survivalists scavenge the predator's kill to provide food for the team; Matt Wright joins the other survivalists and immediately causes a confrontation within the group.

A survivalist sustains a devastating injury, then a vicious storm destroys the survivalists' food supply; both events threaten to tear apart the newly merged camp.

Discovery Channel takes the ubiquitous survival show theme to the next level by stripping it to its bare essentials. In "Naked and Afraid," complete strangers -- usually a man and a woman -- meet in a very unique way: They're stranded in a dangerous, desolate location, without food or water, and they're completely naked. Each episode follows the adventurers as they attempt to survive on their own with nothing but a personal item and the knowledge that the only prize is their pride and sense of accomplishment. Because there is no other choice, competitors quickly get to know one another -- and their surroundings -- and hope that their instincts, survival skills and intestinal fortitude serve them well.

Adventurer Ed Stafford has walked the length of the Amazon River -- he is the first person to accomplish that -- so perhaps being stranded on a desert island near Fiji without clothes, food, water and tools and attempting to survive for 60 days isn't that daunting. The only possessions he does have are cameras, and so viewers are provided a fly-on-the-wall perspective of Ed's attempts to find food, make fire, process water to drink, and build a shelter -- among many other tasks that will help him stay alive.

Surviving in the wild is not an exact science. Beyond the basics of finding water, food, shelter and eventually help, opinions vary. Two experts tell how they think it's done in this series, as initial episodes feature trained survivalists Dave Canterbury and Cody Lundin demonstrating the skills and creative thinking that can help one cope in tough surroundings. Equipped with minimal gear, the pair are left in remote locations -- an uninhabited island off Nova Scotia, a New Zealand mountaintop, deep in the Everglades, the jungle of Thailand, and the desert of Baja California, to name a few -- where they battle the elements and sometimes each other. Season 3 introduces U.S. Special Ops veteran Joseph Teti to replace Canterbury, in the middle of Season 4 primitive survivalist Matt Graham of Discovery's "Dude, You're Screwed" replaces Lundin, and partway through Season 5 producers forge new partnerships by rotating survival experts as hosts.

Extreme survivalists go head to head in a race across the Alaska wild. Using ingenuity, experience and just the gear they can carry in their packs, the participants have 60 hours to reach the finish point of each leg of the adventure -- the series features 13 legs -- and in addition to navigating treacherous glaciated river valleys, barren ridgelines, and high mountain peaks, the challengers battle hunger, dangerous predators and unpredictable weather. There is no grand prize awaiting each leg's winner, other than the pride of accomplishing a grueling feat. For season three, the 12 competitors are divided equally into four teams -- Military, Endurance, Alaskans and Lower 48.

Back to the beautiful state of Alaska for another reality-documentary series, this one set in the Arctic National Wildlife Refuge, a protected area home to thousands of native animals... and a handful of people. In 1980, the U.S. government banned human occupation in the refuge, and only residents in seven permitted cabins are allowed to remain. The series depicts the daily rituals of four families living in isolation and contending with bitter weather, frustrating setbacks, and aggressive wildlife in an unspoiled and unforgiving wilderness. The nonconformists include Heimo Korth, the "godfather of the final frontier," and wife Edna; Bob Harte, who has spent 40 years living by his own rules; and young couple Bob and Ashley Selden, who admit that they've survived by trial and error, learning day by day the harsh reality of frontier living.