Stiff and twisting and random, it reminds her, she says, of the work of another artist represented in the gallery – Nicholas Harding. But not of any of his portraits, although several are in the collection. Instead, Nat Young’s hair recalls the twisted roots and curling lines of Harding’s large ink drawings of Pandanus trees on the north coast.

Engledow, historian and curator at the gallery, says once she made the connection, she became obsessed with the idea of placing the two works side-by-side – Young’s portrait by Albert Falzon, and Harding’s snaking roots. The pairing of the works, while not enough for an exhibition, would be the germ for Arcadia: Sound of the sea, a new show set to open next week. The show is made up of photographs by John Witzig, who co-founded Tracks magazine with Falzon in 1970, alongside seven of Harding’s large-scale drawings and footage from Falzon’s Morning of the Earth, generally considered one of history’s great surf films.

But Arcadia is not an exhibition about surfing, or even about the beach, but a celebration of carefree young men who laugh easily and have a physical beauty unburdened by any responsibility other than riding the waves and having fun.

Engledow had long been fascinated by the work of Witzig, the pioneering Australian surfing photographer.

“His photograph of Mark Richards, taken in 1976, is the most extraordinary photograph of a sportsperson… engaged in his sport,” she said.

“John had to swim out with flippers on, very close to where his friends were surfing, slicing through enormous waves, and just hold the camera out and hope for the best.”

She was intrigued enough by the image to seek out its creator who, now 70, lives alone on the north coast of NSW.

“I found out that he not only had a massive archive of photographs, but he’s a very, very well-organised man, which makes all the difference when it comes to curating an exhibition,” she says.

She also discovered, in the course of exploring the work of Witzig and Harding, that the two men had a mutual appreciation of each other’s work despite having never met.

“It just seemed to me that there was a gentle synergy existing between these two men who’d never met the other, and a real understanding of the kind of strength and gentleness of each other’s work,” she says.

Falzon’s 1971 film adds a third dimension to the show.

“It’s a film of young guys living a life absolutely untrammelled, completely free, shirts off, making their own surfboards, running down to the beach, getting in there and just having a whale of a time,” she says.

In saturated green, gold and copper, the film is infused with a sense of “fantastical innocence”.

“It is a fantasy – nobody could ever have been that beautiful or lived that simply or survived on cabbage and baked beans and done all that surfing, but that’s what they do in the film,” she says.

“And you do believe it, and Alby Falzon himself believed it – it’s life reduced to its absolute fundamentals, and that’s a very strong theme with this show: that engagement with the ocean is a very powerful spiritual experience, an experience of constant renewal.

"We all know that – you go to the beach and your worries do tend to drop away, particularly if you immerse yourself in that ocean and let yourself get dragged around. You realise at once your own significance and your own strength, because you’ve got to survive out there and you’ve got to be bold, particularly these guys on surfboards.”

But while bold and strong, many of the boys and young men in the large-scale, sepia-toned images are bronzed, tousled, cheeky and relaxed – lounging on cars, laughing and enjoying simple pleasures.

“The exhibition is really a tribute to the capacity for a kind of unburdened, uncomplicated fun that young guys have,” she says.

“I’ve always wondered what it would feel like, to walk around with your shirt off… the wind on my chest, as it were. And then, to be so strong, and to be so brave, and just to laugh so easily.”

Engledow, who has written about and curated a diverse range of shows, many of which focusing on women, is not concerned with dredging up cliches about the differences between men’s and women’s humour. She has two sons of her own, but she’s no stranger to her own carefree days and helpless laughter.

“In the show, there is a boyish enthusiasm. When you think of all the cliches that go with the word boyish – boyish enthusiasm, boyish high spirits – that does come through, and I’m not saying anything about girls.”

Aside from the fact that images of 70s babes in bikinis would have made for a different kind of exhibition, the fact is Witzig was shy around girls, and really just photographed his mates.

“He always emphasised that the photographs he took were his mates in places where they happened to be, and some of those guys happened to get famous, others didn’t, and he didn’t care when he was taking the photograph,” she says.

Another ethos underlying the show is the spirit in which Witzig and Falzon – coming from Surf International and Surfing World, respectively – established Tracks magazine, along with David Elphick, who had worked at the pop magazine Go Set.

“They worked out of two hilarious little offices in Whale Beach, and Tracks magazine was entirely their initiative,” she says.

“They found advertisers, they wrote the ads themselves, they took photographs for the ads themselves, they wrote most of the editorial content, although they were constantly pleading for people to contribute articles.”

After a few editions, the trio managed to convinced Consolidated Press to support them – a bold move given the magazine’s anarchic nature, a tabloid-sized paper that was more like a zine than a legitimate magazine.

“They just published pictures of their friends, and wrote articles about their friends, politics, cooking and a lot of articles about the environment and ecological issues, which were very desperate in the early 70s,” she says.

“Rutile mining of beaches, sand-mining, and successive beaches were being torn up, vegetation was bulldozed and so on, and they were very active in complaining about tarring and sealing of roads into secret beaches, and paving of carparks at Whale Beach and Avalon…They ran articles about the death of the Manly Pines and about sewage outfall into the ocean.”

Tracks ran features of how to build your own house and salvage recycled materials, a kind of hippy handbook for those embracing the surfing lifestyle.

Another image in the show, one of the few in colour and one of the few to include a woman, shows a young couple with an infant, sitting at table spread before them with a pile of fresh vegetables. Witzig took the photo while editor of Surf International in 1969, in an issue entitled Country Soul.

“It was encouraging young people, disenchanted with life in the city, to actually make the break, and break with the post-Menzies era expectation that they would get a steady job, that they would get married, that they would have three children, that they would buy a house, and be locked in to the system that suited and still suits most governments today,” she says.

Later, in Tracks magazine, Nat Young himself wrote that “By simply surfing we are supporting the revolution”.

“Even he didn’t really know what he was saying, like a lot of those sloganeering catch-cries,” says Engledow.

“What he meant was, we don’t have to fulfil those expectations.”

The show is also utterly Australian, a fact that ties in well with the so-called short-board revolution happening here from the mid-60s onwards. Australian surfers were experimenting with shorter boards, and simultaneously taking the surfing world by storm.

“That’s not what the show’s about, but that’s part of the background to the show, as is conscription, of course. Many of the young boys presented in this exhibition could have been conscripted and some were. In Tracks magazine, there were letters from soldiers who just wanted to get out into the ocean.”

But, ultimately, the exhibition itself aims to evoke the senses rather than any firm intellectual statements or ideas. Not long ago, Engledow saw an exhibition in Melbourne by a UK artist – an installation that she found “absolutely, totally incomprehensible”. No one seemed to mind this but her. And yet, she says, staging a show in a major institution such as this seems to always require solid explanations and evidence of connecting concepts.

“This show is about textures, it’s about smells, it’s about the texture of neoprene and weatherboards and sand and banksia, salt in the hair,” she says.

“I’ve picked the images that I think are the most beautiful. And they are poignant; the very word ‘arcadia’ carries with it a connotation of a kind of lost world of simplicity and a kind of isolated area where nymphs and shepherds kind of mucked around. Arcadia carries with it a little bit of a connotation of nostalgia, I suppose.”

Arcadia: Sound of the sea opens at the National Portrait Gallery on August 14, and runs until October 19.