A loud voice yelling "High five!" breaks through the roar of the rapids. With that we all turn, raising our paddles like swords and cheering as though we've just had a major victory on some sort of battlefield.
But we're not in medieval Europe; our battlefield is the Tone River, a raging torrent just a couple of hours from Tokyo.
The reason for the celebration is our successful navigation of a tough section of the river but the merriment is short-lived - there's still a long way to go.
The Tone is one of Japan's biggest rivers and it flows through the prefecture of Gunma. This quiet region is generally famed for hot-spring resorts and world-class ski fields and although these two are worthwhile attractions in themselves, I have come here for some springtime adventure in the great outdoors.
Gunma is the ideal place for those in need of a break from the lights of Tokyo, or anyone searching for some action and excitement during their holiday in Japan.
Instead of packing on the weight while indulging in fabulous Japanese cuisine, in Gunma you can burn a few kilojoules while white-water rafting, hiking and cycling through the northern Japanese Alps.
Then, at the end of the day, you can soak away the bumps and bruises while sitting in a hot spring.
The best spot to base yourself for these adventures is the town of Minakami. It's a peaceful and incredibly scenic location with an abundance of accommodation and loads of tourist attractions. Don't be fooled by the calm atmosphere on the streets though.
In the hills and on the water you'll find thrill-seekers aplenty, all getting their adrenalin fix. This is Japan's home of adventure sport and there are several operators in town that specialise in outdoor pursuits. Thankfully, most of them are set up with Westerners in mind, so English-speaking guides are available.
There are two things that dominate the landscape here and, for adventure-lovers, both are worth exploring. First, there's the previously mentioned Tone River, which carves its seaward path through town.
During the spring period from April to June, the river provides consistent grade-four rapids over a 12-kilometre stretch. It forms a fast-moving mass of water with sections of boiling, foamy rapids that have names such as "the dragon's back" and "megawash".
Second, there are the snow-capped mountains that surround the city. With the arrival of warm weather, the snow disappears and the skiers leave the slopes. In their place come hikers, rock climbers and cyclists, making this beautiful part of Japan a genuine four-season resort town.
Because the crystal-clear river is so inviting and the spring weather so warm, my first adventure is rafting. I figure it will be a refreshing means to beat the heat and a good way to take in the natural surrounds. As soon as I'm on the water, however, I quickly discover there's no time for relaxation - you're holding on for your life and getting thrown from one side of the raft to the other.
If you're not so keen on getting wet, head for the hills. There are few better ways to see the Japanese wilderness than in the mountains that surround Minakami. The best place for walking enthusiasts is Mount Tanigawa, a 1977-metre mountain that has perpetual snow. It's one of the largest peaks in the area and features countless trails, all with spectacular scenery.
If you're lucky you might even see one of the resident bears or monkeys that live in the forest. The mountain is also a famed haunt for rock climbers. But be warned; the climbing is treacherous and many lives have been claimed on Tanigawa's cliff faces.
Mountain-bike tour operators offer different levels of trail rides, ranging from tame and mostly flat courses to extreme downhill trails, recommended for only the most experienced. All the necessary equipment is supplied and, as is typical in Japan, safety is paramount.
The guides on any of the tours have a wealth of knowledge and their enthusiasm is overwhelming, making it a lot of fun to spend a day on the Tone River or an afternoon hiking on Mount Tanigawa.
The writer travelled courtesy of Japan National Tourism Organisation, JR East and JAL.
Getting there The fastest and easiest way to Minakami is by bullet train. From Tokyo or Ueno station, take the Joetsu Shinkansen to Jomo Kogen station (travel time is about 72 minutes and costs about ¥5000, $63), then take a bus to Minakami station (about 15 minutes, ¥500).
From Tokyo, drivers should take the Kan-Etsu Expressway to Minakami (travel time is about 2 1/2 hours and costs ¥4000 in tolls).
For accommodation options in Minakami, see tourism-minakami.com.
For more information See outdoorjapan.com and canyons.jp.
- Sydney Morning Herald