Think it's 'just water'? Well, when there's 209,000 cubic feet per second of it... think again. Sure, there's 'lazy' rivers... and then there's big, mean, cold, scary ones – like the ones below. From the Congo to the Citorum, check out seven rivers that will totally kick your butt.
The deepest river on earth
Why it's scary: At a quarter of a kilometre deep at it's deepest point, the Congo is one scary river. Especially when you consider that it's got whirlpools that are big enough to swallow a boat – like the one Steve Fisher is in, above. Add in plenty of treacherous whitewater and death-drop waterfalls, and the Congo could make you soil your shorts.
The highest river on earth
Risks: Seasickness? Try altitude sickness
Why it's scary: Starting at the Angsi Glacier in Western Tibet before dropping into Inida, the Yarlung Tsangpo is the highest major river in the world, with it's source at an altitude that coordinates to over halfway up Everest. Now, you might guess, with that altitude, it would also be the coldest river in the world – but, that's not the case. However...
The coldest river on earth
Temperature: Just above freezing
Fun fact: Surprising short at 220km long
Why it's scary: The Neretva river starts in Bosnia and Herzegovina and flows through Croatia to the Adriatic. Sounds like balmy beach weather, right? Think again. The river is fed by three different alpine glaciers, meaning the water is kept constantly cool – errr, cold. Like one degree Celsius. Get a wetsuit... unless you're this guy.
The steepest river on earth
Rio Santo Domingo
Steepness: If it was a ski slope, it'd be double black diamond
First run: Not until 2013
Other risks: Narcotraficantes (google it!)
When kayaker Rafa Ortiz and his crew descended the Rio Santo Domingo, they claimed the steepest continuous navigable descent in the world. How steep does it get? 2,000 feet per mile, approximately – and make no mistake, that's steep. Not to mention the 20m+ waterfalls.
The longest underground on earth
Sac Actun River
Fun fact: Possible location of Mayan treasures – and dinosaur bones
Discovered in: 1987
We've gone high Tibet and deep in the Congo – now let's go underground. Yes, seriously. The Sac Actun river system in the Yucatan peninsula – which is famous for it's beautiful cenotes – wanders for over 153km through massive underground caves. If you wanna check it out, you're going to need a scuba tank.
The dirtiest river on earth
Pollution level: Off the charts
Can you swim in it? See above
While China's Yellow River is infamously filthy, the Citarum, which flows through Indonesia, takes the cake. Why? To start with, the 5 million people living in the river basin area – and the 2,000 different industries supported by factories there. How thick is the garbage? At places, enough to walk across. However, now that it's recognised as the world's dirtiest river, there's been efforts to clean it up.
Most powerful river waves on earth
Wave size: Easily overhead
Discharge volume: 209,000 cubic feet per second
Things to watch out for: Piranhas and caimans – both bite
Waves? In a river? Yep. When the tidal bore pushes water back against the Amazon's natural flow (which is the biggest in the world, by the way) the opposing forces push the water... well, up. That creates a massive river wave. In fact, it's big enough that legendary waterman Robby Naish can surf it.