The Duchess of Cambridge, 32, dispelled rumours that she was expecting her second baby as she climbed into the Shotover Jet alongside her husband.
Before setting off on the daredevil ride, the boat instructor asked whether anyone was pregnant or suffering from health problems, to which Kate and all others on board remained silent.
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While fashion did not play centre part in Sunday afternoon's engagement, Kate still managed to look flawless in dark skinny jeans and a blue and white checked shirt. The Berkshire-born royal swapped the navy Zara blazer she had been wearing for a waterproof jacket, and strapped on her red life vest that had her title "Duchess of Cambridge" stitched on to the front.
Kate's £79.99 Zara blazer sells out
Kate completed her look with tortoiseshell-printed Ray Ban sunglasses and matched her stunning sapphire and diamond engagement ring with circular diamond drop earrings.
As she and William took their seats at the centre of the jet, flanked by young people who work in the tourism industry, the royal couple waved to spectators. The Duke and Duchess looked to have had the ride of their life as they gripped on to the safety bar, bearing white knuckles and unable to contain their slightly nervous smiles.
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The white-water ride saw William and Kate race past rocky outcrops, jutting boulders and narrow canyons in the shallow waters of the Shotover River — all at a speed of up to 50miles an hour. There were shouts and screams from spectators who watched as William and Kate were given the full hair-raising experience, spinning 180 degrees through the canyons.
After the 25-minute trip, the royals disembarked and broke into applause, clearly thrilled to have taken part in the ride. Kate managed to look picture-perfect even after the twists and bumps, while William's black New Zealand cap was still firmly in place.
As the country that invented the bungee jump, New Zealand is renowned for many things including its addiction to adrenaline sports, and this particular activity takes 130,000 tourists a year down the river.
After completing their fifth and final engagement of the day, it was time for a break from their action-packed schedule. William and Kate headed to the luxurious Matakauri Lodge in the Queenstown area, where they would spend a romantic night for two in a residence overlooking Lake Wakatipu.
The first-time parents had left baby Prince George back in Wellington with his nanny for their overnight stay — the first time they have been apart from their eight-month-old since the start of the tour.