The Duke and Duchess of Cambridge will be just half a metre away from rocks when they ride the adrenalin-fuelled Shotover Jet as part of their trip around the country.
The couple will be taken on the Shotover River jetboat on Sunday afternoon, after steeling themselves for the breath-taking ride with a visit to nearby Amisfield Winery.
The jetboat ride goes through the Shotover River Canyons near Queenstown.
Regional general manager of Ngai Tahu tourism David Kennedy said there was a pool of two drivers, and whichever one was chosen to take the royal couple on the ride wouldn't be holding back because the second in line to the throne and his wife would be on board.
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"[William and Catherine] have requested a normal Shotover Jet boat trip, which is always cautious but it's still the most exciting jetboat ride in the world. "They'll be doing 360-degree spins and going within half a metre of the rocks."
He could not guarantee the couple would get a good drenching on the ride "but potentially there's always a bit of spray that comes into the boat", he said.
The drivers were experienced and had each clocked up "thousands of hours" on the water.
"They're pretty relaxed about the whole thing," he said.
"We're expecting that there'll be some great international coverage - it's an iconic New Zealand product and a New Zealand invention, the jetboat."
There would be extra security deployed along the river and at the base, Mr Kennedy said.
The river would be closed to public for the afternoon on Sunday.
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Tomorrow the Duke and Duchess will be given a tour by Sir Peter Jackson through his collection of classic planes, housed at the Omaka Aviation Heritage Centre in Marlborough.
Sir Peter's spokesman Matt Dravitski said the film-maker had met Prince William before.
"We hosted him here in New Zealand at the time of the Lions tour a few years ago, which was an unofficial visit."
He also met the prince at the premiere of the first Hobbit movie, which was held in London, he said.
A "flying day", with some of the classic planes involved in exhibition flights, would be taking place at the time and would be open to the public, the heritage centre's spokeswoman, Karen Fisher, said.
"They'll look at half a dozen planes ... that belong to the local aviation community here."