On the patio of the house I've moved out of, my soon-to-be ex-wife dribbles a ball, counting down the time. 'Five seconds, four...' Elaine sets her feet and heaves a shot that bows the plastic rim before rattling off. I rebound her miss off the backboard. Luke, our seven-year-old only child, stares at me, befuddled. He isn't used to seeing me in his mother's yard, almost two years after our separation, and is even less used to seeing us horse around as if those years, and the last few of our 11-year marriage, hadn't been deadly. But it's the first mild evening of a belated spring, and Elaine and I are gamely making an effort. Not merely to get on better, but to draw him out of the house, where he is more and more the hostage of his disorder.

Sizing a free throw, I glance at Luke, who has begun to point with both hands to the door. We've been out here five minutes, and already the uh-oh moment, his balky signal that he's had it with novelty. What he wants, with a tireless monomania, is the same thing he's wanted for the past four years: to be alone with his TV/VCR. There, he will swap Elmo tapes in and out of the slot while hopping up and down, flapping his arms. Left alone for any time, he'll strip off his clothes, then alternate between flapping his arms and fondling himself. With my stress level spiking - I am always clenched now, conditioned by his history of seizures and meltdowns to anticipate the worst - I hit upon a thought. Tossing a flat shot off the chest-high rim, I grab the ball and hand it to him. Luke stares at it, turning it this way and that, as if trying to recall this Spalding fellow whose name appears between the seams. 'Jam it!' says his mother. 'Throw it down!' For encouragement, she pelts him with kisses.

He reflects a while longer, looks at both of us, and tosses the ball behind him in the weeds. 'Bye,' he says, and starts up the stairs, unbuttoning himself as he goes. He stops and waves, my receding son. 'Bye,' he says. 'Buh-bye.'

From the beginning the signs were bad, and they worsened as we went forward. Luke was floppy at birth, with muscles so weak his mouth wouldn't latch to his mother's breast. He was late rolling over, later sitting up, and was so late learning to crawl we thought he had cerebral palsy. Those first years were a roundelay of doctors, with each more stumped than the last. Meanwhile, time passed, and Luke's companions stood up on two legs and left him, running after the other kids in the park. Here was a parent's vision of hell: a child whose nameless condition was so dire that two-year-olds had cast him out.

We swept in quickly and found therapists and teachers, getting him home-based treatments early on. Disabled though he was, I was fixed on raising a son who could delight in his body like other kids. Even before he crawled I put him on the floor, rolling balls to him in our master bedroom. He had a natural arm and loved playing catch, though he lacked the least instinct for cupping his hands and seeing the ball safely into his grasp. Still, I took heart and bought him the equipment: a Little Tikes backboard with a weighted base, a football net with a ball he could kick (with help) and a set of oversize bowling pins that he thought were a scream to knock down.

Approaching his third birthday, he suddenly started walking, and our hopes briefly jumped up with him. Soon he was running, and I took him to the park with our trove of balls to try to engage him with boys his age. It worked for a while; he got a kick out of making other kids chase down his errant throws. But one day a boy plucked the ball from his hands, and Luke howled as though he'd been slugged. It was a tantrum from hell, wild-eyed and gasping, the other parents looking on in horror. In a matter of weeks he lost interest in the park, and jerked away when I drove up to it, screaming his one word: 'No!' The greater loss, though, was his pleasure in playing ball, which was replaced by the VCR. Before long he'd doubled his working vocabulary, grunting 'Elmo' (actually, 'Uh-mo') until I caved.

That summer there was another significant development: Luke finally had a proper diagnosis. He has, we learned, a syndrome called Fragile X, a single-gene mutation at the base of the X chromosome that wreaks a range of nervous-system havoc. That flawed gene, identified in 1991 through an outgrowth of the Human Genome Project, fails to make an important protein that regulates other proteins in the brain. No one knows the exact function it serves, but without it key brain cells develop abnormally and their ability to send their signals is impaired. Physical manifestations are, for the most part, innocuous (long faces, prominent ears, and in males, enlarged testes), and kids so afflicted are usually otherwise healthy and can expect to live to old age. But the effect on developing brains is profound, a cure through gene therapy is decades off, and a promising class of experimental drugs is just now entering human trials. For the estimated 90,000 sufferers in America alone, relief is years away.

In its mildest, which is to say rarest, form, Fragile X causes modest retardation and a host of social dysfunctions: shyness, slurred and/or repetitive speech, and obsessive-compulsive behaviours, to name just some. In the middle range, those symptoms are more pronounced and often appended by neuropsychiatric woes: panic, phobias, sleep disorders, and severe overreactions to bright light and loud noises. And then there are the kids in the bottom bracket whose nervous systems are under sensory assault. Picture having to live in a video arcade with the volume and wattage up full, where everyone around you is racing past, speaking Mandarin at the top of their lungs. Your shirt feels like Brillo, your shoes like cement, and the breeze on your skin like the thwack of a soaking towel that's been left to chill in the fridge.

That, in a nutshell, is my little boy, who, like many of his profoundly affected peers, has autism, epilepsy and an IQ we can't measure because he can't, or won't, follow instructions. He is months or possibly years from being toilet-trained, eats with his hands and has no capacity to tie his shoes, though he is Harry Houdini himself at getting out of them.

We have tried (and tried) to ease his symptoms with all the conventional treatments, but have got very little bang for our hard-earned bucks in speech, occupational and physical therapies. The only thing that's helped, and that just barely, is a mix of powerful drugs: Luvox for mood swings, Abilify for attention-deficit problems and Trileptal for seizure disorder. Forty years ago most kids like mine were raised in institutions. Luke may still wind up in a residential school, coming home to Elaine or me on weekends. For now, we're doing all we can to fend that off, day by day.

One night, after an hour of ritualised grovelling to get Luke to sleep, I collapse on the couch to watch TV. Spinning the dial, I happen upon a profile of a man named Izzy Paskowitz. A goateed, lion-maned surfer who was a longboard champion in the early Nineties, Paskowitz runs a bustling surf camp on the beaches of San Diego with his wife Danielle and several of his eight siblings. He and Danielle also founded something called Surfers Healing, a series of travelling one-day surf camps for autistic children. He has a kid so afflicted himself, a boy named Isaiah whose development was normal till he woke at 18 months 'changed totally'. His language was gone, he became agitated and began throwing tantrums that were hard to quell.

Paskowitz, whose father was a champion surfer and who planned on passing the mantle to his son, handled the situation badly for a time. He went out on tour and stayed there for months, living the hang-10 high life of 12ft waves and too much to drink. Returning from the road, he found his wife at her wits' end and his young son 'lost, a different person'. At the beach one day Isaiah was throwing a fit when Izzy had a bold idea. Grabbing his board in one hand and his four-year-old in the other, he jumped in the water and paddled out. Riding his first swell straight into shore, Isaiah grew calm, then exultant. Over days and months of riding point on Izzy's board, a different boy emerged from his cell of symptoms. He began again to talk, his mood improved, and his frustration lessened; clearly there was something tonic about sluicing through water on a shim of fibreglass and foam.

Surfers Healing, born from that eureka moment, has grown into a bona-fide movement. This year, its sixth, it's staging 12 free events in surf towns across America. For some kids it's a one-shot day at the beach; for others, the beginning of a long-term connection to the ocean and its liberating charms.

My first thought, after I blot tears with my sleeve, is to track down Paskowitz's private number and take Luke to San Diego for a week of lessons. But Elaine quite rightly will hear none of it, having flown Luke cross-country before. 'It was non-stop hell,' she says on the phone. 'He slipped out of the seat, screamed, and threw up. It lasted the whole flight back. Either fly the guy here to New York or have him meet you in Florida, but two hours on a plane is Luke's limit.'

Alas, it is April, and the Atlantic is the temperature of rigor mortis. As far south as Virginia it is penguin cold, and there are no waves in Miami. I put in some phone calls: I was looking for someone local, an experienced surfer who has worked with special kids and will have the fortitude to handle Luke's freak-outs. He abhors being touched by people he doesn't know and is acutely fearful of new experiences, which is commonplace among autistics. Add to this the fact that Luke is frightened by waves, and whoever comes along will be sorely tested trying to manage this young boy's terror. To say nothing, of course, of mine.

I grew up a kid whose father left and who experienced his leaving as a death. In a household whose climate was for the most part governed by my manic-depressive mother, my father was the mast that my brother and I clung to, an anchor of sanity and poise. It was he who awoke at two in the morning to nurse me through asthma attacks, chatting while the steam in the bathroom did its work. It was, he explained, to the extent that anyone could then, the logic of my mother's moods. We were intensely bonded, he and I, and then suddenly the Christmas I was nine, he was gone, driven across town by her ultimatums and endless grievances. I saw him on Wednesdays and alternate weekends, but for years I was hollow, a walking cipher. Some holes you fill, and some you don't - not, at least, until you're a father yourself.

Like a lot of men lugging around painful pasts, I had big plans for my son. From birth, if not conception, his brain would be steeped in the amniotic fluid of sports and books. He'd grow up that rarity who could hit a curve and describe it afterward in compound clauses. But the boy I sired proved unable to speak his own name. The despair was like a dead weight on my chest. To lift it, I tried the only thing I knew, which was to get him moving again. I brought him to public pools in Brooklyn, where he flapped and thrashed and clung on tight, refusing to learn to swim. I took him sledding, but our first spill freaked him out and he wouldn't get back on the sled. We drove to the country to hike through the woods and visit a working farm; the smell of cow dung made him sick and he tugged at my arm to go. Everywhere I turned, doors were slamming shut, locking us both in a dingy room, the blinds drawn and Elmo on the TV.

It is impossible to convey what this has meant to me psychically. I have the requisite words, but they will ring hollow if you haven't yourself met great sadness. On the worst days I look into Luke's eyes and find them empty as pools. I know there's life inside them, but don't know how I know; there are times when he's just gone and has left no note.

Two days after my talk with Elaine there is a call from a man who wants to take my son surfing. I have my doubts - I have nothing but doubts - but Elliot Zuckerman won't hear them. 'Your kid will love this. Guaranteed. Never had a kid who didn't, and I've taught hundreds.' Zuckerman, 52, is an ex-pro surfer who grew up riding the chop near New York City. Just past the line where the borough of Queens ends and Long Island's suburbs begin, a sprig of land juts into the Atlantic, forming a sort of bivouac in the sea. Most of the men raised in these sandy flats have been dropping in on waves since they could dress themselves; Zuckerman is the unelected mayor of the beach. He has a frenzied day job as the director of building services for the New York Mercantile Exchange, then comes home at night and spends hours in the water, teaching outlanders from the city how to catch waves. His classes are so popular that a few of the townspeople have come to resent him, so he's tried to limit the size of his groups.

Today, however, this is not a problem; it's just me, Luke and Zuckerman on the sand. There is a good reason we have the place to ourselves: the water is a blue-black 9C. Zuckerman, all chest and cantaloupe shoulders, has already donned his winter wetsuit. Now he has the task of putting my son in one. Luke, as I had dreaded during the drive out here, wants none of it. He kicks, sobs, and arches his back. As we struggle to pull the neoprene past his waist, he pierces me with a look of horror. By the time we get the shin-high boots on his feet and the frog-webbed gloves on his hands, I'm close to tears myself. 'All right, Dad, relax,' says Zuckerman. 'The next time you see him he'll be blissed.'

He picks my son up, grabs the foam-core board, and marches into the four o'clock tide. I hear Luke sobbing till they're 50 yards out, after which there's only the cawing of the gulls. The ocean, as luck has it, is small today, a lumpy blanket of threadbare waves, none of them taller than chest high. In order to get closer to where my son is bobbing, I run out on to a jetty. The rocks are abraded to a glassy finish and a couple of times I almost skid right off them. It is tediously slow going, and before I'm out there Luke has caught his ride. Both he and Zuckerman are on their bellies, barrelling toward shore on a fat four-footer. Luke, whose expression is first stricken, then shocked, suddenly drops into a grin so big I see spray go into his mouth. He is chattering something that I'm close enough to hear, but the world, for some reason, has gone mute. It's a good couple of seconds before I figure out why: I am laughing and sobbing at the top of my lungs while hopping on the rocks in bare feet. There are several teens fishing for trout nearby, and they look me over like some six-toed frog that turned up on their hook. 'Lukey's surfing!' I yell, still pogo-sticking. 'My little boy is surfing!'

I start back to shore, thinking it's over and done with; Luke got his big ride and we can all go home now. This was a lovely idea and we'll definitely return - in August, when it's, you know, summer. But as he and Zuckerman reach the shallows Luke rolls off and stands up. 'More!' he orders, pointing to sea, and to my utter disbelief, out they paddle. For almost an hour they chase waves, catching several good ones all the way in. My heart is in my throat the entire time; this man, a complete stranger, has my child in his arms and has worked some ocean voodoo on his mood. Luke's lips turn blue, then his nose and brow, but damn it all, he's not leaving. Finally, we get him out and peel the wetsuit off him. A huge, dazed smile spreads across his face. 'Yay!' he crows, applauding himself. 'All riiight!' he keeps repeating as I dry him.

That night we go back to Zuckerman's house and set Luke up in the media room. I'm emotionally spent, and when Zuckerman's wife Stephanie asks me how it went, I find myself, for perhaps the first time ever, speechless. Luke is anything but; he runs to the TV screen, naming all the objects that he sees: tree, dog, kite, shade. Suddenly, we can't shut this kid up. He isn't just cheerful or glad to be on land; he's positively thrilled with himself. Snuggling in beside me on the leather sofa, he offers me the back of his head to nuzzle, cackling as I oblige. It is unseemly to kiss your child on another man's couch, and embarrassed, I tender apologies.

'Please,' says Zuckerman. 'Look how happy he is. I've seen it over and over: surfing magic.'

Though the notion of surfing as therapy for autism is so novel that no one has studied it, a number of eminent neuroscientists I talk with later are willing to venture a guess as to why it might work. 'We know that motor-skill learning has a broad-ranging impact on the nervous system,' says William Greenough, an expert on brain development at the Beckman Institute at the University of Illinois, where studies of Fragile X are conducted. 'There's increased blood flow to crucial neurons, and the reshaping of abnormal structures in the front brain. But beyond that, surfing may be a vehicle to an emotional breakthrough, a way of reaching under the mask and perhaps connecting to kids like these.' Peter Vanderklish, a neurobiologist at the Scripps Research Institute in La Jolla, California, who works on the synaptic mechanisms of learning, offers a slightly more personal take. 'I've been surfing for close to 30 years, and my sense is that the sky-and-sea beauty of the sport turns the focus of these kids inside out. They're pulled out of themselves by having to live in the moment, and all their anxieties are pushed aside,' he says.

Since the day five years ago when Zuckerman got a call from the mother of a child with autism, he has surfed, free of charge, with dozens of children who run the clinical gamut. Blind kids, deaf kids, quadriplegics - he has put them in the water, with grand results. 'It's the same thing each time,' he says. 'They panic at first, then get totally amped on the wave.'

Zuckerman, who is friends with Paskowitz, drops everything in early September to host the Long Beach leg of Surfers Healing. He places himself, his surfboards and a dozen or so instructors at the disposal of the day-long event: 'It's like nothing you've ever seen before - between the crowds and media, plus the 60 or 80 families with their kids. They can't stop laughing, or hugging you till it hurts,' he says. 'It's by far the best day of my year.'

He asks us to stay for dinner, but Luke is fading and I need to get him home for his evening meds. Walking to the car, I keep babbling thanks, saying it's been a day I'll never forget. 'Oh, and I meant to ask you, what was Luke saying when you guys caught that first wave in?'

Zuckerman laughs, his big shoulders rolling. 'Well, he was fussing and fighting the whole way out. But when that big wave came and I threw him on the board, he was yelling "Whee, whee, whee!" all the way in.'

For the next couple of days I scarcely know my child. We go to the park and play for an hour, or what he usually spends there in a month. He makes eye contact longer, seems calmer in his skin, and best of all, initiates the roughhouse games that end in hugs and kisses. I call up Zuckerman and book a second session, and one for me. If my son can brave the water in the middle of April, then his dad can cowboy up and wade in, too.

Here, just maybe, is the thing I've pined for: a chance to engage my child at play and develop something that we can do together. I've no experience with balance sports, unless you count the times I tried to downhill ski, tumbling like a drunk in a whisky barrel going over Niagara Falls. And what begins as a charitably warm mid-spring day turns blustery and damp when we reach the beach; no sooner are we in the water than it starts to pour. 'Ignore it,' shouts Zuckerman over the wind-whipped waves. 'Just do what I tell you and you'll have the time of your life.'

He pushes me out to where the sets are forming and turns me around toward shore. 'Remember,' he says, 'come up in one motion! Just pop to your feet and spread 'em!' And with that I'm away, skimming a wash of white foam at what feels like warp speed. My brain yells, 'Stand!' and I gamely try to, but my feet yell, 'Go to hell!' With Samsonesque effort I get to my knees, and suddenly find myself 5ft under, sifting the ocean floor for pretty stones. There is plenty of time to do this, because as soon as one wave lets me up, another right behind it knocks me down.

Zuckerman is unmoved. 'I just told you, no knees,' he rails. 'You wanna start praying, go to church.' He sets me up with a baby wave, letting several curlers pass us by. Again I get about halfway up when the board and I part company for creative reasons. Over the next hour and change I fall in every conceivable way, including several rarely seen by orthopaedists. Zuckerman shakes his head and barks tough-love encouragement, and as I once more succumb to the laws of gravity and their sadistic pranks on new surfers, I imagine him muttering to himself: 'Now which one's disabled again? The son?'

Still, when I clamber out, wring the ocean from my lungs, and collapse on the rain-dark sand, I can't stop grinning. I've never had such fun being an abysmal failure, and want nothing more than to rest a minute, then go back in the water and take my beating. 'Is this what you mean by surf magic?' I ask.

'Well, usually you have to surf to feel the magic,' Zuckerman says, 'but yeah, it's something like that.'

I had always assumed that when I connected with Luke on a sport we both enjoyed, it would be on my turf - a game at which I had some middling skill. But as I drive us out to the beach on Pacific Boulevard the following Friday, it occurs to me that just the reverse has hap pened and I've been dragged, bumbling and stumbling, into his world.

On a surfboard Luke is instantly in his glory, whereas I'm even money for a cracked femur. Perhaps that accounts for my high anxiety as I pull up at the gate. It's one thing to eat it with no one watching, quite another with your boy there. I can only hope he finds my falls funny and doesn't mistake them for seizures.

First Zuckerman, then one of his young assistants, meets us at the beach. The conditions are ripe for our first joint day: small waves, high clouds, and a light puff of breeze that tacks in gently from the south. Today, the Solotaroffs will shred! But Luke throws a fit when he sees the wetsuit, and it takes three of us to get him zipped up tight. It seems grossly unfair to freak him out before he sets foot in the water, but the world is unfair and Elmo can't fix that.

We catch a number of waves, miss a number more, and spend a lot of time in each other's way. At one point I fall, pop my head through the sea foam and see Luke and Zuckerman knifing straight for me. I escape beheading and even get vertical twice, while my son, for all his pique at being shrink-wrapped in rubber, stays in the water for an hour. By the end he and Elliot are a well-oiled unit, going out and coming back in high rotation, wearing loopy grins as they get up. On the drive home to Brooklyn, Luke is silent, staring out of the window in blank exhaustion. So too through dinner of Chinese takeaway, a meal he usually gobbles two-fisted. But in the bathtub he rallies, 'reading' Chicka Chicka Boom Boom , a book he's known by memory since babyhood.

I towel my child dry, that great, painstaking pleasure, pausing to drink his little-boy scent and kiss the down on his neck. He wheels and surprises me with a hug, an act he confirms by yelling, 'Hug!' I hold him so tight it makes my own head reel. Soundlessly we turn an arabesque, a father and young son dancing stag. Carrying him off to bed then, a thought occurs, and I lower him in my arms till he's horizontal. 'Lukey's surfing,' I sing as we sluice the room. 'My brave little boy is surfing.'

He puts his arms out to skim the waves and says, 'Whee, whee, whee' all the way in.?

· For more information, go to: www.surf2live.com; www.surfershealing.org and www.rideawave.org