River guide Joe Kunadei carefully studies the 30-metre-high waterfall thundering down onto the shelf of slippery black lava we're balancing on. "Leave your hat on," he says to me. "It may help the pain in your head." He strides forward with practised confidence, bending ever so slightly at the knees. And then, just like that, he vanishes, consumed in one gulp by the water flow.
Minutes pass, I'm sure he's drowned. Then he appears beside me suddenly, smiling broadly, and hands me a thin rope. "Walk through the waterfall," he says. "You will see." I edge my way further along the slippery rock platform, hoping the frayed rope will take my weight. When I'm close to the cascade I dip my head hesitantly into the downpour. Water pounds the top of my skull, forcing me to my knees. I retreat quickly. "Trust me," Kunadei is bellowing. "Go into the waterfall." Millions of litres of pristine Fijian rainwater plummet onto my cranium. The force of it shocks me; the thin cotton of my cap does little to soften the blows.
The pressure subsides suddenly as I shift my way forward and make it safely inside. I arch my shoulders unnecessarily close to the sheer rock wall behind the waterfall to be sure I'm clear of the torrent. Trapped here, I can just see out. Beyond the gushing water I can make out the gigantic green valley beyond. Rainforest surrounds me, while high above, escarpments of black lava rock rise up in every direction. Guide Pita Nailobau pushes his way through the torrent and joins me against the rock face. He starts to sing softly: an ethereal free-flow of traditional Fijian verse. He closes his eyes, raises his chin and his voice grows louder, until it matches the volume of the waterfall. Locals call the river we're travelling down – whose flow feeds this mighty cascade – the River of Eden. They say this river, the Upper Navua, leads a pathway directly to their ancestors. And here, amongst this cacophony of waterfall and song, I can see the pathway as clear as day.
The Upper Navua River is Fiji's best-kept secret. In an island nation more renowned for its warm, blue sea and white, sandy beaches, the Upper Navua has been largely ignored by all but the small number of subsistence farmers who live beside it, and the few travellers fortunate enough to have made their way down it.
Yet it is one of the South Pacific's most pristine rivers, protected forever by one of the most unique conservation co-operations in the world. Land-owning clans (mataqali), local villagers, a logging company and a rafting company came together 15 years ago to protect the Upper Navua within the Upper Navua Conservation Area. And yet there is so little written about this river that prior to my journey here I couldn't find a word about the adventure I'm taking. Not a single word. In a country visited by 330,000 Australians each year, it's still quite possible to get lost entirely in Fiji.
I'll be taking a raft down the Upper Navua River on a two-day journey through the remote highlands of Fiji's largest island, Viti Levu. While single-day raft adventures have been running along this river for two decades, until now it's been near impossible to camp out overnight along the Upper Navua (my two-day trip will be the first undertaken in almost a year). As of April this year, just one overnight journey per month will pass through here.
The Navua River flows for 65km from the highlands of Viti Levu to the island's south coast. I'm picked up from my resort at Pacific Harbour, 50km west of Suva. We take the coast road west, then head inland along a muddy logging road that winds and climbs its way deep into the highlands. Morning fog lingers atop untouched rainforest as we cross ramshackle wooden bridges. We drive deeper and deeper into the forest till the road becomes unnavigable, then we stop and hike along a path to the river.
Above the Upper Navua, narrow canyons 50 metres high slice straight through endless volcanic rock. The passage seems barely wide enough for our rafts to pass through. Adding to the sense of suffocation is the surrounding forest; huge banyan trees and gigantic green palms and ferns block out the harsh Pacific sunshine.
We push off down the Navua, propelled by its constant flow, bumping off smoothed-out sheer cliff faces. There's over 50 waterfalls in this section of the Upper Navua. As we paddle down it, water gushes at us from every direction: waterfalls, some 60 metres high, pour straight out of the rainforest.
The rapids on the Upper Navua aren't overly threatening or technical (they don't go beyond a grade three rating). While there's enough action to keep thrillseekers satisfied, rafting the Upper Navua is more about sitting back and enjoying the scenery. To cool down, I jump from the raft and swim along the river on my back. Each time I pass a scene as stunning as any I've seen on a river, we round another corner of the Upper Navua and the view is superseded.
"I guess I thought I'd seen what rivers could offer… but honestly no description could prepare me for this," award-winning filmmaker Pete McBride said after rafting the Upper Navua in 2013.
We stop at waterfalls in our path and climb as high as we dare, before leaping like excitable teenagers with our local guides into the river, then eat lunch on sun-drenched, sandy beaches. The South Pacific sun stings my skin, though sudden downpours provide instant relief. Each section of the Navua has its own microclimate; in the early afternoon I'm even drenched by rainfall that buckets down in perfect sunlight. Occasionally I see villagers' clothes stuck in tree branches on the riverbank - evidence of flash flooding that can occur on the river in the wet season - but otherwise there's nothing to suggest anyone's ever made their way through here before us.
By late afternoon we make it to the river camp. Tents are pitched in green undergrowth by a bend in the Upper Navua, beneath a rocky escarpment. Local villagers have dug out a traditional earth oven (lovo) to cook pigs, chickens, taro and freshwater fish caught by guide Moses Batirua on a fishing line behind his raft.
We watch the sun set above the forest from the smooth volcanic rocks on the riverbank, as fruit bats gather above, squealing and stinking up the evening air.
I ride an old wooden longboat upstream to a tiny village set around an old church. Locals live in simple houses built from corrugated iron painted every colour of the rainbow, their washing displayed to all on lines strung between pawpaw trees. Chickens and piglets dodge soccer balls kicked by curly-haired children as the last light of the day turns the Upper Navua golden. As we walk to the village's tiny communal hut our path is lit only by kerosene lamps and candles (electricity comes courtesy of a generator which is run for only hours in a week).
We sit cross-legged on the floor drinking kava with the village chief and his elders. Outside, the sweet stench of hibiscus, frangipani and wild ginger wafts on the muggy evening breeze. When we drink our share of kava we travel back to camp by boat with just the light from a three-quarter moon to guide us home. Our feast awaits us, beneath a clear Pacific sky punctured by shooting stars.
Tents come with mattresses and a pillow, and there's a drop toilet with privacy - provided you remember to place a paddle across the path to let other campers know the bathroom's occupied. We're not roughing it entirely, though neither is this glamping.
At dawn I'm woken by longboats taking children to school. With no roads in these parts, transport comes courtesy of the mighty Navua.
Mist settles on the forest in these quiet moments before sunrise. Soon the sun will burn it off, but for now it's cool, as I sit with my feet in the river, sipping coffee as tiny sparrows circle above me.
Today we'll kayak the remainder of the river, allowing us to negotiate the rapids on our own. A local man on horseback canters past me mid-morning, but otherwise there's nothing but a handful of traditional villages along the riverbanks to suggest we're getting close to the coast.
Waterfalls appear around every bend of the Navua; even this far downstream from the tight chasms of the highlands the scenery doesn't let up for a minute.
Although at our exit point from the river we're just a few minutes' drive from our resort at Pacific Harbour, there's nothing along the Upper Navua to suggest we're part of the modern world at all. The only sign of human habitation are occasional tiny plots of taro or paw-paw, and simple villages devoid of electricity and television.
"This is the real Fiji," guide Joe Kunadei says to me on the second morning as we survey yet another unspoilt green vista. "There's no Coca-Cola or McDonalds here; if you want that, go to Nadi."
Other adventures in Fiji's highlands
River ride Take a jet boat tour along Viti Levu's longest river, the Sigatoka River, visiting tiny, traditional Fijian villages along the way. See www.sigatokariver.com
Village visit Meet the inhabitants of one of Fiji's best preserved traditional villages, Navala, on a day tour into Fiji's remote northern highlands. See www.fiji.travel/activity/navala-full-day-eco-tour
Crater's edge Take a ferry to the island of Ovalau, near Suva, then hike through pristine rainforest to a village on the crater of a volcano. See www.owlfiji.com/epi.htm
Jetstar, Virgin Australia and Fiji Airways fly to Fiji from Sydney, Melbourne and Brisbane from $510 return, see www.jetstar.com.au or call 13 15 38, www.virginaustralia.com.au or call 13 67 89, or www.fijiairways.com or call 1800 230 150.
Sleep in a villa or bure beside three kilometres of white sand beach at The Uprising Beach Resort at Pacific Harbour, see www.uprisingbeachresort.com
Overnight rafting excursions are available once a month from April to September, 2015, and twice in December, 2015. One-day rafting excursions are available every Monday, Wednesday and Friday. See www.riversfiji.com or call 1 209 736 0597.
The writer travelled as a guest of Tourism Fiji.