A man bobs alone in storm-tossed waters, exhausted, struggling to keep his head above the waves. The surface is a froth of wind and rain, and waves break over him. Thunder splits the air, and below it, a deeper sound: the staccato thud of chopper blades. A roaring rotor flattens the water, spraying droplets at his face that sting like BBs. He shouts weakly for help. A U.S. Coast Guard airman stands in an open door 15 feet above the waves, in wetsuit, fins, snorkel, and rescue harness. He plunges in and strikes out toward the drowning man, grabbing him from behind and towing him in a cross-chest carry, kicking hard with his fins.

Just then, the man panics. He flails around, knocking off his rescuer's mask and wrapping his head in a bear hug, trying desperately to climb out of the water. Both men vanish below the waves. After several seconds, the rescue swimmer surfaces, looking about frantically, his mask and snorkel gone. He's broken free, but he's lost his victim. A piercing whistle blows, and the howling wind and rain stop as if on cue. At the push of a button, the thunder stops, the waves slosh down to stillness, and the house lights come up on the U.S. Coast Guard's cavernous new $30 million Rescue Swimmer Training Facility, in Elizabeth City, North Carolina.

Known among Coasties as A-School, this is where enlisted airmen come to test themselves against one of the most grueling training regimens in the armed forces – 18 weeks of relentless physical punishment – hoping to join the elite ranks of the rescue swimmers, among the most fearless first responders on Earth. It is a challenge many of them will fail. Chief Petty Officer Ken Kiest, a burly 50-year-old with a shock of white-blond hair atop an otherwise shaved head, calls the swimmer to the side of the pool. "You let the survivor die; is that correct?" Kiest shouts. "Would you do that in the real world, let my daughter die? You fit to train?" There's no response, and Kiest reddens, shouting louder. "Are you fit to train?" "Yes, Chief Kiest," the swimmer replies. "Obviously your lead instructor says otherwise. Get out of the water." The swimmer hauls himself out and carries his mask and flippers glumly to the locker room. By the end of the week, he'll face a board hearing, and will ultimately be sent "back to the fleet." If he wants to try A-School again, he'll have to reapply and start from the beginning.

Rescue swimmers – properly named "aviation survival technicians" – are a superfit, crazy-brave cadre deployed with the Coast Guard's search-and-rescue helicopter crews. They are trained to save anyone in distress: injured fishermen, sick cruise-ship passengers, raft-bound refugees. To do it, they drop, alone, into nightmare conditions, from subzero waters to hurricane-force winds. During Hurricane Katrina, the Coast Guard, drawing on 80-plus rescue swimmers, rescued more than 33,000 people."When Mom and Pop need to be rescued, we're the professionals," says Kiest, who went through the program himself in 1990. "In emergency, break glass and pull out Coast Guard."

Kiest loves to show off the bells and whistles of the 50,000-square-foot facility. Besides the wave generator, there are spray nozzles for creating sheets of rain, even a fog machine. A touchscreen controls dozens of sound effects: rotors, jets, foghorns, machine guns, sirens, and three kinds of thunder. The massive fans can stir up a 70-knot wind, the equivalent of a Category 1 hurricane. To demonstrate, Kiest cranks them to full blast, the winds lashing the surface of the water. Towels fly off the bleachers on the far side of the pool. A rope course above the pool is modeled after the Navy SEALs', and a parachute hangs from a winch, to practice saving downed aviators. In another pool, a device known as the Dunker trains strapped-in pilots to escape from submerged and flipped-over helicopters and boats.

The "noncompliant survivor" is just one of the tests rescue candidates must pass in the 18-week program. After this, they'll face the downed-pilot parachute rescue and various "multis," during which they must deal with as many as six victims in the water at once. But the noncompliant-survivor test is the first and often the last test for many airmen. If the candidates can't get their victim safely under control and hoisted to the platform by rescue harness within the seven-minute limit, they'll fail A-School. Attrition is merciless: Eight weeks in and nine of the 18 hopefuls have already failed.

Next on the platform is Josh Piasecki, a 21-year-old airman from Rogers, Arkansas, whose wide-set eyes and muscled frame give him a distinct resemblance to a pit bull. Kiest fires up the waves and thunder again, and the "drowning man" – an instructor named Stephen Gonzalez, jumps back into the water and begins to flail helplessly. Piasecki jumps in, swims strongly and smoothly and gets the uncooperative Gonzalez under control, even when he ducks Piasecki underwater. In a few minutes, Piasecki has a harness around his victim, he's clipped them in, and the two of them are hoisted, dripping, from the water.

Kiest looks on from the pool's controls in silent approval. Sometimes Kiest can tell who in a class will be his standout "show pony"; sometimes he's surprised when an underdog candidate makes a breakthrough. "It's a butt whipper, physically," he says. "But if you've got it mentally, you've got it." His show pony, in this class, is Piasecki – he's scary strong and more confident in the water than any of the others – though Kiest would never tell him that. For Piasecki, the Coast Guard promised more adventure than college life had; one day in his sophomore year, he dropped out and joined up. "I wanted to join the military," he says, "but I didn't think I could shoot at somebody, so I joined the Coast Guard." He knew he wanted to try out to be a rescue swimmer. Piasecki wasn't a strong swimmer when he enlisted, with little more sea experience than wakeboarding on a lake back home, but no other gig in the Coast Guard offered as many adrenalized thrills as jumping out of helicopters to save people did. He'd trained for months to qualify for A-School, hoping to one day take part in the sorts of legendary Coast Guard rescues he'd heard about.

Rattling the candidates' confidence and breaking down their comfort is a big part of the instructors' technique. "It's the game they play," says candidate Joe Foss. "They're all masters of psychology." Adam Via, 28, a lanky, buzz-cut-blond Californian, stands a head above the class. "It's tough," he says. "They picked on me at first – and they ripped into me good." Today he sports an angry scrape on his face from his underwater bout with the noncompliant survivor. Via had indeed gotten off to a rough start. "I did not expect to see him here past week three," says Petty Officer Jason Jennison. But Via surprised him. "He's progressively been getting better every time. He's got good heart." As Jennison puts it, "We can teach all the stuff, but we can't teach 'Don't panic,' and that's really what it comes down to: thinking under stress and not panicking."

While much of the training aims to develop "water confidence" – the ability to think clearly and act decisively in the harshest marine environments – panic, or at least some serious nervousness, weighs on the minds of the class. In the next few days, they'll have to take their make-or-break final noncompliant-survivor test. They will have three opportunities to complete the test in less than seven minutes, or they'll fail. Even worse, they'll all be tested on Jennison, who clocks in at 230 pounds. It will be like trying to swim while shouldering an ox. After so much exhausting effort, no one wants to consider the prospect of failing now and having to take the course again, but in A-School failure is an ever-looming possibility.

The average attrition rate of the program is 50 percent, but it varies wildly among classes. The class ahead of Via and Piasecki's, which is just about to graduate, began with 15 members and has only three left. Senior Chief George Marinkov, A-School's 52-year-old director – who appears to be chiseled out of granite – was one of only two members of his class to graduate.

The candidates follow a strict daily regimen of physical conditioning, practicing rescue skills, and coursework, starting at 7 am for up to three hours of dry-land training. Then they get in the water, where Kiest puts the group through excruciating physical paces. They swim sidestroke while holding a 10-pound brick aloft in one hand. "Buddy tows," pulling a partner in cross-chest carry for hundreds of yards, follow. Then they drop their bricks 12 feet to the bottom, shuttling them forward as far as they can before surfacing for a single breath of air. Kiest watches closely to make sure nobody takes two. He knows that no amount of instruction can prepare a class for the endless unpredictability of ocean rescues with life-or-death consequences. As if to remind himself of this, he has a tattoo on his calf: a pair of fins, a snorkel, and a mask clipped to a rescue hook, emblazoned with the A-School graduation numbers of the four swimmers who have died in the line of duty since the program's inception in 1984. The notion of self-sacrifice as the highest sort of valor is deeply held in the Rescue Swimmer community. It's even in their motto: "So others may live."

One of the most dramatic examples of their mission occurred 100 miles due east of here, on October 29, 2012, during the devastation of Hurricane Sandy. Rescue swimmer Randy Haba was asleep on a couch in the Elizabeth City air station's lounge when an emergency page came in at 4:45 am. A vessel off Cape Hatteras was taking on water. It was the HMS 'Bounty,' a three-masted, 180-foot wooden tall ship, built in 1960 for the Marlon Brando epic 'Mutiny on the Bounty.' There had been 16 people aboard. The crew had been forced to abandon ship. Daniel Todd, another rescue swimmer, was called in from home.

Ninety minutes later, hovering at 30 feet above raging 30-foot seas, with 75-mile-an-hour wind gusts, Haba was lowered by cable into the house-high waves. He swam to one crew member who was floating alone in his survival suit, semiconscious. Haba placed him in a rescue basket, and they were both hoisted from the waves. Haba was then lowered toward a life raft, rescuing four more crew members. Meanwhile, Todd was lowered into the same colossal waves, swimming to the side of a life raft and calling out, "Hi, I'm Dan. I heard you guys need a ride." (President Obama would repeat that story a few days later.) Todd rescued the remaining survivors. One crew member was found dead several hours later. Despite a 90-hour, 12,000-square-mile search, the captain of the 'Bounty' was never found.

For this A-School class, the noncompliant survivor test proves to be a heartbreaker. Of the five candidates left, two manage to rescue Jennison and pass the test: Piasecki and Via. Even for them, there will be many more tests in the weeks before they graduate, but they're over the hump. And after graduation, there's EMT school, and Advanced Helicopter Rescue-Swimmer School, where they'll learn techniques for high-seas, cliff, and sea-cave rescues. They still have a journey before they're deployed. For the other candidates, failing is a deep disappointment after so much suffering. But it's not necessarily the end. Weeks later, Piasecki wrote in an email: "Most of them will try again; to have made it this far into the training, you have to be pretty dead-set on why you want to be here, and failing out is more of a motivator than a deterrent."

As punishing as the program is, every instructor knows how much rougher and less predictable the ocean can be. For all its thunder and wind, the A-School pool is still a highly controlled environment within which to assess a swimmer's stress and endurance. As Randy Haba says, "If you have any doubts, it's better to find out here."