In the waning decades of the 20th century, men from New Zealand began inventing new ways to injure themselves. They jumped from bridges with elastic bands attached to their ankles, ran class-five rapids without boats, and fixed themselves to large kites to achieve great speed. Soon enough, a culture had emerged—one that paired backyard engineering with the pursuit of adrenaline. Today, thanks to these pioneers, brave souls the world over may hurtle through the air, down mountains and up rivers and live to brag about it. In their own words, the inventors explain how extreme sport on this island nation came to be, and where it might go next.PART I: ORIGINS,(1954-1980) A sheep farmer builds an engine to travel upriver–and starts a high-speed revolution.We’re way at the end of the bloody world. Back then, if you wanted to do something, you had to do it yourself.TREVOR GAMBLE (creator, “thrill” jet boating): Has anyone told you about the number-eight-wire mentality? HENRY VAN ASCH (co-inventor, bungee): The Europeans who came here 200 years ago were hearty, efficient people. They figured out how to live off the land.GEORGE DAVISON (engineer, Hamilton Jet): We’re way at the end of the bloody world. Back then, if you wanted to do something, you had to do it yourself.ANDREW AKERS (inventor, Zorbing): The sheep farmers always had number-eight fencing wire lying around. You could fix anything with that. It was the duct tape of the olden days. MATT BECKETT (manager, Blokart): It’s the number-eight-wire mentality.PETER LYNN (inventor, kite buggy): There are two ends to the innovation spectrum. At one end are developments like the Manhattan Project, which require huge state-supported programs and have specific goals. At the other end is the solitary inventor. New Zealand may well have punched above its weight in this category.STEVE WEIDMANN (inventor, Sky-Jump): Also, you’ve got the rugged landscape here—lots of mountains and rivers.LYNN: Innovation mirrors lifestyle. We’re closer to the outdoors here.GAMBLE: We’ve got a bunch of braided rivers that you can’t get up with a regular boat. You can’t have anything sticking beneath the water, like a propeller.PAUL BECKETT (inventor, Blokart): The guy who created the jet boat was a sheep farmer down south.DAVISON: He was trying to figure out a way to get upriver to go fishing.GAMBLE: Really, all he did was create a water pump. It sucked the water up through the boat and shot it out through the transom at the back end. It’s a simple principle: Velocity plus weight equals thrust. This was 1954.AVISON: Bill was like me, a country boy off the farm. When he was young, he fiddled with machines and boats, bits and pieces around the farm. Someone showed him a photo of the Hanley hydro jet, a centrifugal pump they used on a few fire boats in the U.S. Bill built a copy. It didn’t go well. It had an elbow nozzle just beyond the intake. It spoiled the thrust and had a hell of a lot of drag. So they changed it. They stuck the nozzle straight out the back, so now it sucked up water through the intake and shot it out through the air.TONY KEAN (author, The Ballad of Bill Hamilton): Lo and behold, the speed doubled! And now there was nothing sticking out the bottom. They did an expedition up the Colorado through the Grand Canyon. The jet boat really took off from there.DAVISON: By 1960, there were a lot of jet boats around here. People used them for climbing through shallow rapids.GAMBLE: There was this business giving sightseeing tours on the Shotover River. I paid $11,110 for it. Mind you, I had never driven a boat of any kind in my life. This was 1970. That first year, I ran the river the way it had always been run. After so many trips, I started going faster, tried to get as close as I could to the rocks. But a couple of people complained, so I dialed it back. The third year, this older woman—she had to have been 73, 74—said in the middle of the trip, “This is so disappointing! I went down last year, and it was much more thrilling.” After that, I just started driving straight at the rocks. I did a 180, a 360. I credit that woman with completely turning us around.