Three men in kayaks cruise along Mexico's Usumacinta River, a light cross breeze rippling its brilliant teal surface. Erik Weihenmayer pilots the center boat, a cobalt-hulled, eight-and-a-half-foot Liquid Logic Stomper 90, outfitted for long distance. He takes even, powerful strokes, sending tiny droplets flying off his center-bent Werner paddles, as his colleagues, Rob Raker, 58, and Chris Wiegand, 40, move briskly with him in tight formation. Wiegand leads in a compact yellow freestyle boat; Raker is right behind Weihenmayer, sitting deep in a weathered red hardshell, beaming behind aviator shades.

"Lookin' good, Big E!" Raker roars – both to Weihenmayer and to the spectacular wilderness. Weihenmayer's slight wry smile in response offsets the impression he gives, with his burly frame, brooding looks, and multi-impact helmet, of an NHL enforcer on vacation.

The half-dozen other men in their group are scattered ahead and behind along this winding river in Mexico's remote southeastern corner, where they've just begun an intensive, weeklong kayak training run. Only their laughter carries over the wide expanse of water to the high rain forest walls, where it is quickly eaten by jungle chatter and the deep, nightmarish roars of the howler monkeys that inspired the Mayan name Usumacinta, or "Sacred Monkey River." No one watching these three kayakers would notice anything unusual about them. But few could imagine what Weihenmayer is doing – or has been doing for most of his life.

(Courtesy Erik Weihenmayer)

The 45-year-old pro adventurer is best known as the only blind person to climb Mount Everest, in 2001, a feat that landed him on the cover of Time at age 32 and made him an international symbol of courage. Weihenmayer also solo skydives and paraglides. He skis double-black slopes and backcountry. He and a small team raced a dozen others across the deserts of Morocco. He has climbed each of mountaineering's vaunted Seven Summits and scaled the 3,000-foot rock face of Yosemite's El Capitan, along with the 2,000-foot, technically tougher frozen Himalayan waterfall Losar.

But despite these achievements, this trip down the Usumacinta has Weihenmayer seriously considering his limitations. For one thing, there's the fact that he's a blind man kayaking. "I've often thought, 'Why am I doing this?' " he says. "This is not what a blind person should be doing." Then again, his sighted companions probably shouldn't be doing this, either.

The Usumacinta happens to run through Mexico's conflict-ridden state of Chiapas and along the border with Guatemala – a region where crocodiles, narcos, and banditos limit traffic to paddlers who are more than slightly adventurous. When Weihenmayer's crew trained here just over a year ago, one tricky canyon passage provided the added thrill of an RPG missile whizzing overhead.

They've returned to prepare Weihenmayer for something scarier than close-proximity military ordnance, and everyone is ferociously dedicated to helping him succeed – or at least survive. This September, in what may be his toughest in a life of self-imposed impossible missions, Weihenmayer will attempt to kayak the entire length of the Grand Canyon. He will put in at Lee's Ferry, nine miles south of the Arizona-Utah border, and paddle 277 miles of the Colorado River: through 15-foot waves, 26-foot falls, and school bus–size whirlpools, facing 200-odd rapids with names like Upset and Specter, plus the hundred unnamed others that would merit a "Satan's Maw" or "Deadman's Neck" on any other river.

It's an inadvisable trip without Class IV rapids skills, an insane one without sight, and Weihenmayer will undertake it with probably the sole human who's as blind and nuts as he is, military vet Lonnie Bedwell. The 49-year-old Indiana native lost his sight in a 1997 hunting accident and went on a gung-ho sortie down the Grand Canyon River last summer with veterans group Team River Runner, with whom he'd learned to kayak just one year earlier. While surviving the trip won Bedwell the distinction of being the Grand Canyon's first blind kayaker, his and Weihenmayer's September trip will be profoundly different – a crew of the world's top kayakers have joined in Weihenmayer's near-samurai mode of achieving the impossible.

Weihenmayer regards the Grand Canyon challenge as less a test of mettle than of a discipline and philosophy he has lived by for nearly two decades. "I mean, I know I can survive it," he says of the run. "But I climbed for 10 years before I did Everest. I feel like I should build up in a classic way to these big endeavors in the world."

Consider a snapshot from the summer of 1995, when Weihenmayer – then a 27-year-old teacher at an Arizona elementary school – walked onto a sunbaked playing field with an arctic mountain tent, plopped down, donned polar mountaineering gloves, and, in 100-degree heat, began erecting and dismantling the tent for hours on end until he had the task down to just a few minutes.

He'd struggled with the tent on a recent climb up Mount Rainier, and since his fingers pinch-hit for his eyes, he'd removed one glove for just long enough to locate a tent seam – and felt his hand freeze into an agonized cinder block before it even touched fabric. On the mountain that day, he made a pledge that he'd later recount in his memoir, Touch the Top of the World: "The things I could not do, I would let go; but the things I could do, I would learn to do well."

Eighteen years and dozens of summits later, the things he's painstakingly mastered are too numerous and various to count. It's clear that his blindness opened up extraordinary reserves of creativity and discipline. At the same time, he reflexively bats away most direct praise. "I get the focus for being the 'blind kayaker,' ?" Weihenmayer told me. "But Rob, Chris, and my other guides are totally consumed. Instead of their own kayaking, they're watching this little remote-control guy going down the river and completely manipulating his destiny." He refines the analogy: "A little remote-control guy who doesn't do expected things; a video game with a bad joystick and a glitch in the software."

But here on the Usumacinta, it's apparent that this little remote-control guy will have to kayak better and more instinctively than most sighted paddlers. Right now, Team Big E is locking into gear: Point man Wiegand scans downstream for white flumes or surface rotation, tasked with finding "the line" of green water running through the white chaos and away from holes, boils, haystacks, and other hydraulic terrors that kayakers euphemistically call features. Raker, the rear guide, follows both the line and Weihenmayer's movements, a round foam headset microphone by his mouth ready to transmit commands like "hard paddle right" and "hard-paddle left" the instant they need to be executed.

Today's trip is intentionally free of any hard-core paddling. As with high-altitude climbing, the early stages of serious kayak­ing are about acclimatization more than distance, with each new launch requiring an autonomic adjustment. "Kayaking is really more neurological than muscular," says Wiegand. "A lot of people think it's about physical strength – overpowering the force of the rapids – but really, you want to be neuroskeletal: nimble, reflexive, relaxed. Even in total chaos, it should be intuitive."

But chaos is on the itinerary. The charted rapids on the Usumacinta reach Class IV, and uncharted dangers can appear with little warning – less if you can't see. Last year, Weihenmayer's first run down the Usumacinta left him so spun out, he considered quitting the sport entirely.

"The whirlpools and the boils were really crazy," he says. "I got in over my head. I was paddling as hard as I could, and I couldn't get anywhere; this whirlpool was still sucking my boat in." Eventually, he was forced to "swim" – kayak parlance for the gasping, bobbing struggle that follows whitewater ejection – and even on dry land found his body wouldn't let him get back into his boat. "I was so adrenalized I could barely stand," he says. "That made me go, 'I don't know if I can get comfortable in this environment.' "

Instead of quitting, he improved his skills, undertaking additional expeditions in Colorado and Brazil, and logging four long days on the artificial rapids at the U.S. Whitewater Center, in Charlotte, North Carolina. There, Raker and two Olympic kayakers drilled Weihenmayer on his combat roll, his draw stroke, and the other skills he'd need to survive the overwhelming force they call big water.

"[Kayaking] is right in his trajectory," says pro mountaineer Jeff Evans, Weihenmayer's guide on Everest and a dozen other mountains. "That's how he's wired. It's not just kayaking – it's everything. He needs to see what he's capable of. He wants to be scared."

In this, at least, he has succeeded. "More than anything else I've ever done, kayaking has made me work to somehow get a hold of my fear and panic," says Weihenmayer. "To really have discipline over my mind is by far the hardest thing I've ever done."An abrupt tropicaL sunset ends our first day on the Usumacinta, and the team is dug into the shoreline for the night. Along a steep and cratered wedge of sand, men are securing tents, sipping rum, applying weapons-grade bug repellent, and switching on their LED headlamps as the black rain forest swallows the last of the light – all but the one kayaker who never needs a flashlight. Cast in the glow of a small campfire, Weihenmayer is a quietly arresting presence, his physical brawn offset by a quick tenor and the fixed-eye expression of a perpetually quizzical geology prof.

"Mountains are slow," he says. "You're plodding up the rock face – it's about power and endurance. With kayaking, you have this crazy, powerful environment happening underneath you, this thing that's like a fifth element, that does crazy things that are hard to understand and impossible to anticipate. Eddies go in opposite directions, waves hit you in weird directions, and holes suck you down when you aren't expecting it. It feels like going into a battlefield."

The environment has come to trigger a combat-like response in Weihenmayer's body. "The other month, I threw up just at the sound of the rapid below me," says Weihenmayer. "Now I'm at this point where I'm having dreams – where I'm kayaking and I don't have a guide, and I'm, like, flying down, down this crazy rapid, and I can hear these giant walls around me, and I'm like, 'I got no guide,' and I hear this noise . . . ." While Weihenmayer now calls kayaking "10 times scarier than the scariest thing I've ever done," he is someone who's been doing scary things practically since birth.

When Weihenmayer was an infant, his jittery eye movement sent him and his parents to nearly a dozen different eye doctors over two years before they got a diagnosis of juvenile retinoschisis, a rare hereditary condition that causes the retinas to disintegrate. "The doctor said, 'I'm sorry to inform you that your son will be blind by the age of 13,' " recalls Weihenmayer's father, Ed, who later had to tell a boy who'd just learned to walk that he'd go blind before reaching high school.

The youngest of three boys born to an ex-Marine and Princeton football star, Weihenmayer didn't go gently. While his disease robbed him of his central vision, it spared the peripheral long enough for him to choose a life strategy of denial over adaptation. "In seventh or eighth grade, I'd look way up or way down as I walked," he says, recalling navigating solely with his remaining peripheral vision. "I was a little shit to my Braille teacher because learning Braille would mean I was blind, and I didn't want anything to do with blindness." His father recalls him tossing a white cane off a bridge to get run over by oncoming traffic.

On the grade school basketball court, Weihenmayer's jump shot was decent, his aim was terrible, "but he was just crazy on zone defense," says his dad. On the streets of his hometown of Weston, Connecticut, he'd tear along on his bike and do jumps on two homemade bike-stunt ramps, furiously pedaling dead at them until the stage when he could barely see the ramps – at which point his father spray-painted them bright orange. "It probably gave him three or four months of being able to be Evil Knievel," says Ed. "He just fought to stay in the sighted world."

Losing this fight enabled Erik's first true victory. Deteriorating vision kept him from participating in most school sports, but as a totally blind freshman, he made the high school wrestling team. This was thanks in part to an enlightened coach who showed no mercy to the 5-foot-9, 114-pound blind kid, letting him get pummeled and slammed to the mat hundreds of times before he won his first match. "I'd actually rate his innate athletic ability above-average," says Ed. "But his focus, perseverance, and stamina are A-triple-plus." By his senior year, he'd become the team captain and competed in 1987's National Freestyle Wrestling Championships in Iowa. He had discovered the first thing he could do exceptionally well without sight.

He discovered the second the next summer, when a blind camp sent him to a rock-climbing course in North Conway, New Hampshire. A counselor taught him and his mates a mode of echolocation common to most blind people: listening for the precise collisions of sounds that delineate a space's topography, then creating a mental map of their surroundings. But once they roped and harnessed at the base of Cathedral Ledge, the climbing instructor told them not to get their hopes up. He wasn't sure if ears, hands, and feet could substitute for a climber's eyes.

While his peers tapped out after a few valiant efforts, Weihenmayer nearly scurried up the first ascent, earning the nickname Monkey Boy. He almost immediately intuited an alternative rock-climbing strategy. "What I like about rock climbing is that I can't see the hold," he says. "So I have to scan my hand across the face in a systematic, grid-like way," adding that the system has a dynamic pace. "I don't have time to hang out. One arm is locked off, and I'm losing energy as I scan. But then I start finding patterns – if this crack is moving up to the right, it might open up into a handhold. Nature doesn't give up its patterns very easily, but you can find them if you're really looking. And it feels amazing when you do."

At the top of his first summit, North Conway's Whitehorse Ledge, Weihenmayer had a vivid realization. "I could hear all the way down into civilization," he says. "I could hear all that huge open space. And I remember thinking, 'Fucking A, I can do this. This is adventure. It's everything I envisioned.' "

Weihenmayer's challenges as a kid didn't end with blindness. "His mom was a fierce advocate for him," his father recalls. But in 1985, his father arrived at Weihenmayer's summer camp to inform him his mother had just been killed in a car accident – a blow Weihenmayer calls "worse than going blind a thousand times." Ed Weihenmayer tried to cope by planning a three-week bonding trek at some exotic locale with his three sons.

"Erik was the one who said, 'We should do the Inca Trail in Machu Picchu,' " says Ed. A few years later, after convincing a guide to let a 19-year-old college freshman be the first blind person to make the trek, the Weihenmayers flew to Peru, and Weihenmayer stumblingly, painfully hiked the entire Inca Trail, beginning to develop the system that he'd use to scale Mount Everest.

"I'd sort of be steering Erik with my hand on his shoulder," recalls Ed. "So we'd hit a root or miss a step and go tumbling off the trail and wind up all bloody and scratched." Neither one found this much fun. "Hiking in Peru was a miserable struggle because I didn't know how to do it," says Weihenmayer. "We were just stumbling along, and we didn't have the right system or tools."

His older brother Mark took over their dad's guiding duties, with a looser hold and more explicit trail directions, and the two took on increasingly difficult treks around the world, hiking across Tajikistan's Pamir Mountains, Pakistan's Karakoram range, and the Indonesian province West Papua.

In 2004, Weihenmayer flew to Lhasa to lead an expedition up Mount Everest's north side with six teenagers from the first and only blind school in the region, which a blind German social worker had founded against local opposition. "The Buddhist culture there says that you did something bad in a previous life, so you deserve this blindness," Weihenmayer says. "That attitude is a part of a lot of Third World cultures."

(Photograph by Jamie Kripke)

Years ago, Weihenmayer's understanding of such cultures inspired him to found the No Barriers organization, a nonprofit that helps facilitate adventures for blind children around the world. But off the podium and Oprah's couch – Weihenmayer has been a guest on national programs ranging from Larry King to The Tonight Show – he's a far cry from the relentlessly upbeat, slightly dopey, indomitable spirit of after-school specials. "He's very witty and clever, and he knows how to push people's buttons," says Jeff Evans. "And he can use that distant stare to kind of add to that 'F you.' "

A huge tropic moon hangs over the Usumacinta. The campsite is quiet, the fire is dying, and Weihenmayer decides to begin making his way over the steep, deeply cratered shoreline to his tent. Half rising to leave, he waves one level arm out in a searching sweep that I interrupt to ask what he's looking for.

I'm pretty sure I see the Weihenmayer "F you" play briefly across his features, as he continues his perimeter sweep. He utters a soft, ironic "Ohhh, what do you think?" – then taps and snatches up the same Leki hiking pole he's used to navigate every inch of our trip thus far. Which had been standing planted in sand right in front of my big dumb face.

"G'night!"By 10 am, the sun has set the campsite sand ablaze, as Weihenmayer's crew cinches up rubber dry bags and lashes gear to hardshells, preparing for their second day. Weihenmayer stands at the shoreline, conferring with two others about the river. "See that eddy line right over there?" he says at one point, then raises a trekking pole and points directly at a subtle demarcation in the rapids 30-odd yards away.

Still blinking sleep from my eyes as I try to locate the eddy line, it takes me a moment to remember that Weihenmayer can't actually see it. He had used his hearing to pick up the distinctly pitched rush of an eddy line and used it to update a mental map of the surroundings. "You get into this mode where you totally forget he's blind," says his wife, Ellie. "You're in the airport and you're looking back and you're like, 'Oh, my God, somebody go get Erik.' "

Weihenmayer met Ellie Reeves in 1993, when they were both teachers at the prestigious Phoenix Country Day School, a job he took for easy access to better climbing. As Weihenmayer thrived teaching English and math to fifth graders, his secret romance with Reeves was exposed by his guide dog, Wizard, who began back-burning guiding duties to track Ellie in the halls. She and Weihenmayer were married and now live in Golden, Colorado, with two children: Emma, their 13-year-old daughter, and Arjun, the 10-year-old son they adopted from a Kathmandu orphanage in 2008.

At Phoenix Country Day, Weihenmayer also met a substitute teacher named Sam Bridgham, who became his rock-climbing partner. Some time early into their partnership, Bridgham suggested they scale the highest peak in North America. "I thought Sam was a lunatic," Weihenmayer recalls of hearing his buddy's proposal they take on Alaska's Mount McKinley, known to alpinists by its Athabascan name, Denali, for "the Big One."

Pro mountaineer Evans, who'd met Bridgham on an EMT wilderness course, also assumed Bridgham was joking about a blind climber who was ready for Denali. But when Sam drove Weihenmayer out to Evans' home near Joshua Tree, California, he agreed to bring him rock climbing. "I didn't know how good he was," Evans says. "But he just kept crushing each route I took him on." By sunset, the two had finished the toughest climb in the area. "And I'm like, 'Well, the sun's down – why don't we head down to camp and drink a beer?' And he looked me straight in the eyes and said, 'You think I give a shit that the sun's gone down?' ?" Evans sparked a headlamp, and the two kept climbing until three in the morning. "I knew all he needed was a team that would commit to him and to doing something big," he says.

They enlisted the seasoned mountain guide Chris Morris to lead them on Denali, began an intensive training regimen, and went on team-building ascents of Washington's Mount Rainer and Colorado's Longs Peak, mastering belaying, crevasse rescues, and other skills. They set off for Denali in June of 1995, enduring a 19-day climb up the 20,320-foot peak – an elevation gain greater than Everest's – during which members of two other teams died and a third's became paraplegic.

Six years later, Weihenmayer stood atop Everest and expanded the world's sense of possibility.

Then he kept going. In 2002, he became one of the 350 humans who have scaled the Seven Summits. A year later, he became the sole blind member of the 50-odd other lunatics who completed the brutal 457-mile adventure race called Primal Quest. In 2008, he climbed the Carstensz Pyramid, and in 2010 he completed the hundred-mile Leadville 100 mountain bike race.

In 2008, Weihenmayer was a passenger on a Grand Canyon whitewater rafting trip with Global Explorers, acting as mentor to a small group of blind and sighted kids. The river guide was a man named Harlan Taney, who at one point asked Weihenmayer if he wanted to try paddling an inflatable kayak he'd brought along. Weihenmayer jumped in and the two set off using the first in what would prove to be an ever-more-complex series of guidance systems: Taney's orange plastic rescue whistle.

Weihenmayer recalls it as love at first touch. "I loved being in my own boat," he says. "I loved being independent. And I loved the rapids just hitting you out of nowhere, as you blasted through those waves and reacted. I was a total novice. I didn't understand what made up rapids, how they worked; it was all so new."

Later, Weihenmayer asked Rob Raker, whom he'd met in 2000 at base camp on Antarctica's Mount Vinson, to teach him how to kayak. A seasoned paddler, Raker showed Weihenmayer some basics in a pool, then took him on a trip through a narrow canyon on Idaho's Green River called the Gates of Lodore, again leading Weihenmayer with a whistle and shouts. Around this time, former Olympic kayak coach Wiegand reached out. "I didn't even know he was kayaking," says Wiegand. "I just saw an article about him, saw him speak, and was like, 'This guy is incredible.' "

Wiegand joined Weihenmayer and Raker on a trip down a different section of the Green River, in Utah's Desolation Canyon, one of the most remote areas in the continental United States. In this forbidding environment, they first tried upgrading their guidance system with two-way radios.

Three years later, Weihenmayer sits beached by the Usumacinta in his sun-baked kayak, black wetsuit on, red helmet off, face lowered as if in prayer. Standing 15 feet away, Raker calls out, "Weihenmayer, can you hear me?"

Weihenmayer puts a hand to the earpiece of his black radio headset. "I can't hear a thing," he says. "Can you hear me?"

"No."

Raker looks at a black module on his waist. "Mine's blinking blue," he says. The team's tech specialist steps in. "You have to hold it down for, like, five seconds to shut it off," he says.

As Raker says "test-test-test" into his mic, Weihenmayer fiddles with the headset's Velcro strap. Finally Weihenmayer declares, "This thing sucks. Too floppy; throw it out – fuckin' Brits," miming a prima donna's disgusted toss, then softly answers Raker through his mic: "That's pretty clear."

Weihenmayer's jokes cover jagged nerves. Today's run will reunite him with one of the rapids that caused him a neurological collapse last year: La Cola Diablo, "the Devil's Tail," which contains a feature with the appropriately existential designation of a "hole." Unlike whirlpools – which merely flip you, spin you, and release you – holes don't let you go. They pull your boat down stern-first into their spinning maw, where it might end up for weeks with the trees, debris, and other kayaks spinning in its so-called grinder.

Weihenmayer says that when La Cola Diablo grabbed his boat, "I got frazzled and twitchy." And even when he got out of the boat, his body wouldn't calm. "It looked like a seizure," says Wiegand. "You get spasticity issues, and the whole nervous system starts overfiring. That's when it gets dangerous. If he were asked to walk a straight line at that point, he'd fall."

Weihenmayer has since gotten a better feel for the confounding behavior of whitewater, whose complex systems of fluid dynamics often make it seem like a living, breathing entity. For a blind person, this incredibly data-rich sonic world of a whirlpool can almost literally drown them in sound. In steep rock canyons, echoes turn a run down the rapids into a headlong sprint through a hall of mirrors and make sensory navigation a form of psyops torture. Though he's one sense short of a full five, Weihenmayer describes the effect as "sensory overload."

This afternoon, Weihenmayer has to push such memories aside as he paddles past the gorgeous Cascada Busiljá waterfalls, around a graceful bend, and toward the Usumacinta's first big water at La Cola Diablo. Here, two main currents meet and gush over a two-foot rock ledge, creating the giant swirling hole marked by two white flumes, which look like mortar bursts from a hundred yards away.Weihenmayer moves smoothly toward those white flumes and drives straight into a six-foot wave. His bow smartly salutes, and he sails into the Devil's Tail. This time, he hits the swirling hole and gives only one reflexive jerk, regaining control by giving in to the whirlpool's swirling circular motion like a driver turning into the skid of a hydroplaning car. He takes its current into his body, passes it along, rotates with and out of the hole – then speeds straight into the darkening water below.

Four or five kayakers encircle Weihenmayer's boat, all bearing smiles. Weihenmayer doesn't know exactly what he did differently. "It's not your conscious brain reacting," he says. "Last year, I know I was not reacting well, not leaning the right way. This time, I hit the wave and it . . . just worked. The whole thing is sort of in my fiber."

Hours later, at night, the crew gathers after dinner. The fire glows, the tequila flows, and talk turns to matters of the latrine. Each one is a connoisseur of the finer malarias, dry heaves, diarrheas, and parasites of the natural world. Taney describes a parasitic fluke he picked up in Africa and the damage done.

"When I got to the CDC, they wouldn't diagnose me because they said I hadn't 'properly preserved the specimen,' " he says.

Soon they're laughing over a boastful friend who guides expeditions on Kilimanjaro, and I blurt out, "He sounds like Commander McBragg," referencing an obscure, walrus-mustached, Kiplingesque character from the Underdog cartoon show. At the mention of the name, Weihenmayer goes into a fusty Victorian British accent.

"There I was. Surrounded by 10,000 Chinese. So I dove off the Great Wall of China, into the Sang Po. And I swam across, fighting the crocodiles, and found a giant piece of bamboo, which allowed me to pogo stick over the Great Wall into Tibet . . . where I was saved."

Weihenmayer, it turns out, watches television and movies, in a more expansive usage of the verb you quickly get used to. He liked Life of Pi, found Skyfall decent and Moonrise Kingdom overrated. Aided by his wife's running account of visual action, he takes in dialogue, performances, music, sound design, and narrative.

Weihenmayer caught his last few crucial glimpses of the visual world as he entered adolescence. The last TV show he ever saw, with one eye pressed against the screen, was a Real People episode on Canadian athlete Terry Fox, who lost a leg to cancer and, in the hospital, decided to run across his nation. "I'd never heard of an athlete with a disability doing something that just blew your mind so hard," says Weihenmayer. "Most people in that situation retreat; they go, 'Oh, my God, I just gotta survive.' Terry did the opposite – he attacked. I know I had him in mind when my dad asked if I wanted to do a program that taught blind kids to rock climb."Weihenmayer's loved ones often find watching what he does unbearable. "When we saw him climb McKinley, it was nauseating," says Ellie, who'd flown to Alaska to support him. "It's one thing to hear about it," she says. "But when I looked up to where he was, I wasn't looking high enough. I took a couple steps back, looked way up, and it was – it was hard to witness. With kayaking, it's the same thing. I can only hold my breath so long while he's under there."

Ellie would not enjoy the sight of Canyon San José, right near the end of our Usumacinta trip. Its jagged black limestone cliffs rise into the mist like the first appearance of Skull Island in King Kong, and mark the entrance to one of the trip's most fearsome rapids. Called La Linea – it's the line dividing Mexico from Guatemala – the rapid is filled with crisscrossing currents, scores of colliding eddies, and whirlpools that seem to pop from every spot.

At the foaming top of La Linea, Wiegand and Weihenmayer burst into view, coming down fast, with Raker right on their tail. Over the rapids' din, you can hear Raker yelling: "Forward! Forward!" Weihenmayer adjusts his course and drives on. His trip is far from smooth – a series of micro corrections that jitteringly execute Wiegand's commands and follow the line.

He does not cut a heroic figure in the kayak: hunched forward, eyes inert, head cocked, expression unlike his teammates' ESPN-ready, tendon-clenching squints. His face suggests the sublime concentration of someone tuning out deafening noise to take directions from some other, liminal source.

Farther downstream, past the boiling descent and unfathomable physics of La Linea, a wide green circle spreads out deep in the canyon's bend. Wiegand, Weihenmayer, and Raker slide into the pool like it's the hay-strewn landing of a carnival ride. Half their party is still upstream, helping an expert Mexican kayaker in the group who got rolled and was forced to swim by the same rapids Weihenmayer just navigated without sight.

Big E has many months of training before he navigates the Grand Canyon, and his skills and equilibrium will never improve enough for him to have the careless thrill sighted kayakers might enjoy. But Evans, who personally guided Weihenmayer to the top of the world in 2001, says strength, skill, and courage aren't the sole requirements for people like him and his teammates. "What we say is, 'You have to suffer well,' " says Evans. Weihenmayer has had more practice in this than most people ever will.

But that's clearly not what he's finding now on the Usumacinta, where whoops and laughter echo from deep at the base of black limestone cliffs.

Harlan Taney blasts into the eddy pool and swoops up to join Team Big E as it exults. "He nailed it!" yells Raker, his throaty voice echoing up the high rock walls. "That was beautiful!" calls Wiegand, joining the din.

Later, Weihenmayer will say, "I'm not trying to confront death. It's an awesome environment. There's a gift there. All the craziness and chaos and fear is what you have to fight through to get that gift." Now the cheering friends meet in the wide green eddy, and the four pull in tighter, kayaks nose to nose around Weihenmayer's center, the quartet slowly rotating in the green water, their faces beaming, the pitch and tone of their voices sounding jubilant.

But the rush of water is too loud for anyone but them to hear what they're saying.