I'm gripping the grab rail with both hands on an exciting white-knuckle ride down the fastest-flowing navigable river in New Zealand and have forgotten what century I'm in.
Swift-flowing grade three rapids and two Lexus V8 engines producing 560hp, are carrying me through ancient beech forest on a wild, weaving, winding, 27-kilometre ride down the Wairaurahiri River from Lake Hauroko to the sea, through Fiordland National Park.
Giant overhanging trees thrust out gnarled, moss-covered branches over the river, taunting me when I stand up to feel the fresh, cool breeze in my hair.
The river bed is strewn with tree trunks transformed by time and tannin stains into grotesque shapes. Great boulders smoothed and rounded by ice-age glaciers, rise up to meet the speeding jet boat, threatening to capsize the craft.
At regular intervals the dense forest opens up to reveal a catastrophic landslide of grey/blue mudstone and precarious undercut cliffs of ash-like papa rock, where the raging torrent has strived to escape the confines of its banks.
I can't escape the feeling that riding this bush-bound river is like travelling back in time to a prehistoric era long before man sought to tame the wilderness of the Waitutu Forest.
Fortunately this area escaped the early forest fires and logging gangs and remains under the control of a Maori Trust with no plans for its exploitation. It is now the largest tract of unmodified temperate lowland forest left in New Zealand.
"This place is a national treasure that must be preserved at all cost," skipper Johan Groters tells our small group of adventurers.
"Today's journey down the river should be a straightforward trip unless things turn to custard. We don't want to hit any big boulders as it's a three-day walk out of here."
Johan has the understated, pithy humour and matter-of-fact machismo of a Southern Man who has seen it all and knows what he's about after twenty years on the river. If we are going to have a dispute with a river boulder I feel confident he would soon slip into Man versus Wild mode and see us right.
I'm now acutely aware of the profusion of boulders in this river, which drops a staggering 200 metres across its length. We skim past Lonely Rock, which has drawn less skilful drivers into its lovelorn clutches.
The manoeuvrability and responsiveness of the twin-engine jet boat is amazing, as the craft turns violently around the bends, slewing sideways and skidding over the surface, defying all hidden obstacles confidently riding on its 12mm aluminium bottom reinforced with grader-blade-quality steel.
We nose into a quiet backwater and step ashore to examine one of Johan's many stoat traps placed along the river banks. He demonstrates the spring mechanism and his ingenious flag alert system that tells him when a trap has been sprung. These traps can be sponsored by the public as part of Johan's award-wining stoat control programme.
Deep inside this river section of the Waitutu Forest are the remains of 150 live deer capture pens. The pen gates were set under spring tension and released when deer walked into the trip wire.
I'm incredulous when told that the men led the animals on a rope over rough tracks back to the waiting jet boats. The stoic, laconic Southern Men that immortalised the Kiwi approbation 'Good on ya Mate' must have originated in those halcyon days of the 1960s.
Before we leave the forest glade I can't resist a photo session. The beech trees are laden with soft, spongy mosses and I have a real sense that this is everyone's vision of an enchanted forest.
The tree limbs assume weird shapes with their mossy cloaks and the whole scene is so arrestingly beautiful that I can't believe that the forest is inhabited by deer, possums and stoats - not goblins, elves and fairies.
Back on the river, time stands still once more until we suddenly burst out on the dramatic panorama of Foveaux Strait. Bouncing over the river mouth we float for a time on the open sea before crossing the bar and nosing into a quiet beach and stepping ashore.
What we find is an idyllic clearing in the bush, remarkable for its vivid green grass, which we learn is cropped and manicured each night by browsing deer.
Fronting the clearing is the two-storey Waitutu Lodge and a separate caretaker's lodge occupied by Alastair Osbourne (alias 'Peanut'), who has lived a solitary existence here for nine years with his constant companion Max, a black and white collie dog.
This man of the bush, traps possums, goes whitebaiting in season and hunts for his own pork and venison, sparing his mates the red deer hinds that mow his lawn on a nightly roster. An electrician by trade, he used to service lighthouses in remote areas. This colourful character is renowned for his firmly-held opinions on most subjects and visitors appreciate his company.
On cold nights on this hard edge of the southern landscape, Peanut is part of the Waitutu Lodge experience. Later I learn that he is planning on returning to civilisation permanently.
A tasty Kiwi lunch of venison, sausages and salad is laid out before us and we are joined by four mud-splattered, hearty Australian trampers who will join us on the trip back. They have traversed the Hump Ridge and Port Craig tracks and are loud in their praise of this pristine wilderness.
Our return journey up the river is surprisingly smooth as the jet boat is able to maintain a slower, steadier speed against the current. Reaching Lake Hauroko we find that its mood has darkened. The lake is cold and deep, wild and free. Its restless spirit has been stirred, whipping up into an endless succession of foam-tipped swells.
"This is New Zealand's deepest lake at 632 metres and the seventeenth deepest of the world's five million lakes," Johan informs us.
He adds with a grin: "It's so deep there should be grouper down there."
Arriving at the ramp, Johan drives the boat onto the trailer. We head back to Clifden, passing pass through the Lilburn Valley and the westernmost farm in the country, ending an exceptionally thrilling journey into the heart of remote Fiordland.
We have explored an untouched wilderness and listened to an informative commentary, making this a true eco-tourism journey. The scenery, the local characters and the heart-thumping ride make the whole Wairaurahiri Jet experience better than any theme park.
What to do: The Wairaurahiri Jet operates from Johan Groters' home base at 1260 Clifden-Orawia Road, just over the Clifden Bridge, 20 minutes drive from Tuatapere. The trip's duration is 6.5 hours and warm clothing and rainwear is recommended as the weather is quite changeable around Lake Hauroko.
Where to stay: Accommodation in Tuatapere is available at very reasonable rates in the Waiau Hotel, 47 Main Street, along with warm southern hospitality and country cook fare.
Paul Rush travelled to Lake Hauroko courtesy of Venture Southland and Wairaurahiri Jet.