Freedivers are all about diving as far down as they can, ever trying to beat the last great attempt. They don't wear oxygen tanks -- they voluntarily deal in apnea, the cessation of breath. They dive down either with their own power, aided by weights, or strapping themselves into a machine known as "no limits," and come up at the last second with a balloon-style flotation device -- basically an Opposite Day parachute.

Wendy Timmermans/Total Free Dive

Wendy Timmermans/Total Free Dive

These are people who have painstakingly taught themselves to survive up to 9 minutes, 24 seconds without air, and it is precisely as dangerous as it sounds: There are around 5,000 freedivers in the world, and an estimated 100 of them die every year. That's 2 percent of your entire sport just up and dying on an annual basis, and the people who perish are not just overconfident rookies: In 2015, Natalia Molchanova, the greatest superstar of the sport, never surfaced from a freedive that she was doing just for shits and giggles.

At that depth, shits and giggles are both fatal.

"Now, hold on," you're surely saying. "If it's just a contest to see who can hold their breath the longest, why not do it in a small tank of water, where they can easily sit up if they exceed their limits?" Oh, you naive fool. You're still not getting it: It's because freedivers are fucking crazy. Understand, the body changes in many ways when you go hundreds of feet deep with no air but what you hold in your body. In some competitions, half of the divers come up unconscious. A study of 57 freedivers in an eight-day competition saw a whopping 35 of them suffer from some "adverse event" or another due to the body freaking out because of the lack of air.

Which makes sense, as their body is all but completely failing on these dives. Like a robot running out of battery, the typical freediver's heart slows down to just 14 beats per minute, as opposed to the normal human heartbeat of 60 to 100 beats per minute. People in a coma have a faster beat. You shouldn't be able to maintain consciousness, let alone operate at that level. In fact, experts reportedly have little idea how 100 percent of the divers don't wind up unconscious on these dives.

Yet they push on, despite -- or because of -- the insanely high mortality rate and the fact that science has no idea how they're doing their thing.

The 30-mile swim between the Farallon Islands and San Francisco's Golden Gate Bridge is 10 miles longer than the English Channel route, but that's just part of its terrorizing charm. The course goes straight through an area called the Red Triangle, a fun area of the ocean with the greatest number of great white shark attacks on humans. Shockingly, this means that anyone stupid/courageous enough to attempt the Farallon-Golden Gate route risks having to cut their swim short for little things like, oh, suddenly noticing that a great white shark has started circling them.

Sharks are banned from all but the most exciting Olympic events.

But the sharks aren't your real enemy -- you're far more likely to succumb to water that can get as chilly as 48 degrees, and if that doesn't sound very cold to you, it's because you've never been submerged in 48-degree water for hours. It's cold enough to suck the heat out of the body so fast that you'll go into shock and won't be able to control your breathing. One early attempter's body temperature got so low that, when his support ship fished him out, the nurse on scene initially declared him dead.

And then there's the weather. The route has a portion nicknamed the Potato Patch, known for its unpredictable, huge swells. Riding the waves on the Potato Patch can be like getting tossed off a 10-story building (80 to 100 feet at their peak), and its many currents, shifts, and whirlpools can be like you've fallen into God's washing machine during the spin cycle. That is what the Farallon-Golden Gate swimmers are trying to swim through ... after already swimming for hours, after already having seen all of their limbs go numb from the freezing cold.

Kathleen Jacques
Actual frost zombies have refused to compete.

But hey, screw sharks, cold, and waves, right? Surely modern technology has plenty of wetsuit with cold repellents, shark repellents, and wave ... repellents that enable a strong swimmer to power through the route? Well, they might ... if it wasn't for the fact that whatever maniac set the rules for the swim declared that to officially complete this route, you aren't even allowed a wetsuit. You'll be jumping in the freezing, watery sharknado wearing just a bathing suit, goggles, and a swimming cap. We're kind of surprised they even allow that.

What you wouldn't expect is a mind-numbing hamster wheel race around a single city block in New York. But that's what the Self-Transcendence 3,100 Mile Race is all about, and that's what the few dedicated super-runners willing to take part in the competition face: endless laps around a single block in a boring cityscape, on a ruthless concrete surface. For 52 days, their day starts at 6 a.m. They run (or walk) until midnight, trying their best to complete all the required miles before the time limit is up. Do the math, and that's basically two marathons a day, every day, for almost two months.

So unless they're willing to cut down on their daily six-hour break, there's no fun with friends, no TV, no shopping, no video games, just monotonous running on the same stretch of dreary New York streets. And yeah, this isn't even the interesting streets -- the block is a boring-ass one in Jamaica, Queens, creating a course of a little under .55 miles. It's like purgatory for runners.

courir-en-auvergne.fr
Purgajoggy.

Some of the runners are in it just because they like to run. Most of them are disciples of the Bengali Guru Sri Chinmoy, and believe that part of spirituality is taking on seemingly impossible physical challenges. Regardless of their motivation, this race might not make headlines with crazy injuries or deaths, but it's still pretty hard on the feet ... literally. Runners go through a dozen pairs of shoes during the race, and because no shoe feels good for long on a two-marathons-per-day pace, they generally just give up and cut the toe area away, letting their toes enjoy the sunshine. As for the ones who don't, well ... one runner had to have all of his toenails removed, because it was either that or the toes as well. He took a little two-hour break, and then resumed his race.

Then there's the matter of diet. The runners estimate they burn through 10,000 calories per day, so they need intensely calorie-rich foods to keep from withering away, so they pretty much need to be snacking all the time. Said snacks, by the way, range from simple apples and glasses of (non-alcoholic) beer to freaking sticks of butter.

tycoon751/iStock/Getty Images
"No time to stop and chew, just give it to me as a suppository."

Still, with their shoes giving up under them and nourished by things that would down a lesser person, the runners blaze on. The race has taken place regardless of the conditions; one year, New York was suffering such an insane heat wave that the mayor declared a "heat emergency" and estimated there would be 140 heat-related deaths in the city. The race went on as planned, though presumably the participants had to ingest their butter from a cup.

The universe of Mad Max is one of those gloriously madcap fictional worlds that are gorgeous to look at but might be somewhat unpleasant to actually live in. Real-life limitations and common sense render it borderline impossible to re-create Fury Road-style massive, deadly car chases where crazy people ride awesome custom vehicles through never-ending deserts. That is, unless you count the Dakar Rally, which just so happens to be that exact thing.

Andre Lavadinho/A Vialatte/ASO
Dakar is Senegal's word for "vulture chow."

The 3,000-mile Dakar Rally used to be between Paris and Dakar, Senegal, but had to be moved to South America in 2009 because of terrorism threats. You can take part with pretty much any land vehicle you fancy, from trucks and normal cars to motorcycles and quads. It's a two-week off-road race with speeds averaging 100 miles per hour, and unholy insanity is pretty much its status quo. Since its inception in 1978, the Dakar Rally has claimed over 50 lives.

Red Bull

Red Bull

Red Bull

The ways it can kill your ass are varied and plentiful: People have died of heat stroke, heart attacks, and thirst, or a combination of all three plus terror caused by simply getting lost. Spectators aren't any safer: In this year's rally, 10 people were injured right off the bat when an out-of-control car went careening into the stands. That's right: This is a race that isn't even safe to watch.

Andre Lavadinho/A Vialatte/ASO
The photographer is this picture's only confirmed survivor.

It's called the Jungle Marathon, which is a much more descriptive name than "freediving" but still undersells exactly what madness is taking place. For one thing, a marathon is 26.2 miles -- this one is a seven-day, 137-mile trek. So, more than five of those. The "jungle" part is accurate, though -- you're doing the whole jaunt through the Amazon, the long-reigning champion in the "green hell" weight class of geographical hellholes.

Fabio Andrade
The knee-high swamp wins in the "brown-hell" class.

So, in this particular competition, your race is not so much for the prize as it is for getting to the goal in one piece, and your most dangerous opponent is Mother Nature herself. Participants face challenges like the Jaguar Alley, a portion of the race that goes through known jaguar territory, where runners are advised to avoid running too far away from each other and armed guards stand watch at night (yes, of course they stay overnight in the area. How else could the jaguars get a sporting chance?) To date, no one has been eaten by a jaguar (as far as we know), but multiple people have seen them, and more than one competitor has reported being stalked by them.

The race directors do their best to make sure the journey is safe-ish, but as shitty as humanly possible; after all, this is an extreme sports event, so things tend to -- and are meant to -- leave sports competition territory and veer screaming into disaster-movie land. Not that they have to try too hard. The most recurring attacks from the local fauna come from wasps, which pretty much attack every single runner in the race. It's not unheard of for a runner to limp on with 18 stingers sticking out of them.

Other wildlife that takes little to no shit from human passersby include supersized ants, ticks, snakes, and venomous scorpions. There have even been multiple reports of freaking stingray attacks (yes, you're splashing through water in many parts of the race). Or maybe nothing will sting or bite you, and you just have to escape an angry wild pig by climbing up a tree. Did we mention that many trees in the Amazon are poisonous and can cause numbness just from touching them? Good luck running with a body you can no longer feel, buster! On the other hand, not feeling your legs might be a good thing, because the jungle does a person's body absolutely no favors.

Jungle Marathon
"Why, peeling and discarding excess toes doesn't hurt at all!"

And then there's the heat and humidity, which by itself would make the run a nightmare even if all other conditions were ideal. You don't get help, either -- competitors have to haul their own gear throughout the race. As such, the completion rate of the Jungle Marathon is predictably low: In 2012, 60 people started the race. Only 11 managed to finish it in full. And that's picking from a group of people already willing to travel around the world to compete in such an event in the first place -- the craziest of the crazy, in other words.

We like to imagine the other 49 people took two steps into the jungle, stopped, blinked, and said, "Wait, what the fuck am I doing?"

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For as long as competitions have been a thing, there have been those who just need to make them infinitely more painful to perform. See what we mean in The 6 Most Terrifying Historical Car Races and 5 Bizarrely Masochistic Races People Run For 'Fun'.

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Did you know cats modeled their "meow" after the cries of human babies, just because they knew us humans care about that noise? Did you know dogs can read your mind (emotionally), and live in constant suspicion that you know where the good food is (you totally do)? In the next LIVE episode of the Cracked Podcast, host Jack O'Brien leads Cracked's team of pet-loving/fearing comedians through all the ways our dogs and cats are more powerful, creepy, and awesome than we ever could have imagined. Jack will be joined by Carmen Angelica, Dan O'Brien, Alex Schmidt, and Jake Weisman at the UCB Sunset Theatre on Wednesday, March 9, at 7 p.m. Purchase your tickets here!