Number seven really surprised us, although we suppose we should have known better! Check out these hazardous bodies of water. You may not even know what dangers lurk in your area of the world!

1. Rio Tinto is among the most acidic bodies of water around, with a pH balance of 2, at best. This means the Rio Tinto is as strong as stomach acid and is more than powerful enough to kill any fish that dare swim in it. Most likely, it would do the same to humans.

2. Oregon’s Tualatin River is not the place to be if you want to take your dogs for a swim; close to a dozen pups die there every year from exposure to toxic blue-green algae. Actually a deadly form of bacteria, algae can grow fast, quickly polluting a body of water in a deceptively pretty shade of turquoise. Those unfortunate enough to swallow the stuff can expect sickness and diarrhea at best, paralysis and death at worst.

3. Here we have a body of water that can destroy us, but only because we screwed it up. Citarum River might well be the most polluted, trash-filled bit of water on the planet. Thanks to more than 500 factories that line the river, plus the area’s lack of trash collection or modern plumbing, the river has filled with waste and rubbish to the point where you can barely see the water.

4. Whoever named this place was certainly no fan of subtlety: Boiling Lake is exactly what it sounds like. Discovered in 1870 by two Englishmen, temperatures taken five years later ranged anywhere from 82 to 91.5 °C (180 to 197 °F). While that’s certainly hot enough to peel skin, those temperatures were only recorded around the edges of the lake. The center is far, far hotter—to the point where an accurate measurement cannot be taken, lest the guy with the thermometer get boiled alive.

5. Catching E. coli is no fun under normal circumstances; now imagine you were literally swimming in the stuff. That’s the reality around various rivers in Johannesburg, South Africa, where the amount of E. coli bacteria in the water is way beyond acceptable levels. Some areas, like the nearby Cheetah Bridge, host 240 times more E. coli than what is considered healthy. The more fit-and-trim areas, such as Kaalspruit, only exceed the healthy limit by 190 times.

6. Like a supermodel with a bomb strapped underneath her bodice, Russia’s Lake Karachay is pristine, gorgeous, and incredibly deadly. It is, without question, the most radioactive body of water on the planet. A major dumping ground for nuclear waste until the ’90s, Karachay’s toxicity was so bad that, for a long time, you didn’t even have to touch the water for it to kill you. Simply standing on the shore for an hour or so would bombard you with 600 roentgen of radiation. Most humans die from 500 roentgen over five hours, for comparison’s sake.

7. Though the only thing most people know about the Potomac is that Washington, DC is situated on it, the legendary river can also be associated with something else: horrible deaths. The area between Great Falls and Chain Bridge forms a series of rapids and waterfalls that send their victims spiraling downward for almost an entire 1.5 kilometers (1 mi). If that’s not enough, the river’s strongest currents are actually underwater, so if you get sucked down, you stay down.

To read more about these deadly rivers, lakes and waterways go to Listverse.

The next time you are walking around your favorite water source, be it a small lake or even a mysterious swimming pool, you may want to check for a sign that read: DANGER!

We may never look at a river the same ever again!