The Mountain to Sea Cycleway and Blue Duck Lodge are helping but a monster legend (or successful movie) could really rev-up local tourism. And as mythical creature yarns go, this one seems as compelling as anything from the Scottish Highlands. During the 1930s it was written up in an academic journal; descendants of some of the men attacked apparently still live in Taumarunui and - for sheer appeal - the groovy watercolour painting of the alleged incident gazumps those drab (faked) black and white photos of Nessie.
The monster attacked the surveyors on a farm now owned by the Atihau Whanganui Incorporation.
We found the spot using directions from a 1937 article published in The Journal of the Polynesian Society (an academic quarterly that's still around) by Thomas William Downes. Downes knew the men involved and from their recollections painted the watercolour, which now hangs in the Alexander Turnbull Library.
Article and painting are available online but oddly enough none of the locals we met on our travels knew a thing about the story.
Arriving at the property, and having gained permission to enter it, we prudently left the Mini at the farm gate. A retired Retaruke farmer who knew the river well, the late Doug McFadyen, crammed into a ute with us and our other guides, local farmers Michael and Joan Petersen. We had to make a tricky 100-plus metre descent to the Kawhautahi Stream, then hike about 15 minutes to the lagoon.
So on the way I went over what little we knew ...
More than 120 years ago as a Pakeha surveyor named Charles Taylor persuaded three Taumarunui Maori - Warahi (Wallace), Pita te Aitua, and Piki - to work for him as linesmen and chainmen at a location called the Waimarino Block.
Taumarunui historian Ron Cooke tracked down a photo of Te Whiutahi Warahi and Te Huia Pikikotuku, whose descendants still live in the district.
The track leading to the taniwha lagoon led past this appropriately spooky house.
The Maori, who believed a man-eating taniwha held sway over the area they were heading to, were uneasy.
"In the old days none of their ancestors would go near, yet when the Waimarino Block was being surveyed, and the Pakeha laughed at them for being frightened, some Maoris decided to risk it for the big money being offered," said Downes.
"The men worked all the first morning cutting lines through the scrub and raupo and had almost forgotten their fear when Warahi happened to get a glimpse of the lake.
"There was the taniwha rushing toward him on the surface of the water with the speed of a galloping horse.
The Mini parked at the entrance to the rough and steep track leading down to Kawhautahi Stream lagoon, 100m below.
"Warahi cried out the alarm. One glance and all the men went in different directions, fleeing for their lives through the flax and swamp.
"The European was the worst off as he had his heavy instruments, which he did not wish to lose, but in trying to save them he slipped and cut his leg badly with a slasher.
He lay quiet for a time and as he found he had eluded the taniwha he tied up his wound with strips of his shirt and then crawled back to the camp, which he reached the same night.
Michael and Joan Petersen briefly paused our taniwha hunt to inspect a wild pig caught by two of their young neighbours. The late Retaruke farmer Doug McFadyen is standing in the background.
"Pita and Piki also reached the camp later on that night, but they were covered with cuts and scratches and their clothes were practically torn off them.
For three days no one would venture out of the camp, not even the Pakeha. But on the fourth morning the Maori men went out to search for their companion whom they eventually found unable to walk and quite dazed.
"Also, there were marks of the scratches of the taniwha all over his body; he must have been caught and left for dead but he himself could never remember what had taken place.
Each of the Maoris affirmed that Kawhautahi chased them, and they certainly believed it.
The theodolite, chain, and slashers remain at the lakeside to this day," said Downes.
Well, we found the lagoon but not the discarded gear, and though it would be theatrical to report a sense of foreboding as we hiked along, the opposite was the case. It had fined up following a storm and the area is stunningly beautiful, with magical-looking trees bearded with lichen.
The Kawhautahi Stream leads to a lagoon, reputed to be the home of the ferocious taniwha of the same name.
Except for the background, the lagoon did look vaguely like the one in the painting. To video it, I stood on a clod of earth which began to sink into the deep pool.
Somehow black shags get fresh water mussels at this spot. Large mussel shells were all around the lagoon's edge and reputedly enormous eels live there too. The water boiled with native trout, rising to feed on tiny pieces of meat Joan threw in while the video was running.
Verdict: Loveliest riverside spot imaginable but of the gnarled old maneater - not a peep.
• Paul Charman was a guest of Wairakei Resort Taupo, and was loaned the Mini by BMW Group NZ.