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Water covers 70% of our planet, providing us with life-sustaining benefits like hydration, recreation, and agriculture. But not all waters are friendly—some lakes and rivers can be hazardous, capable of causing harm, sickness, or even death.
10. Rio Tinto, Spain
The Rio Tinto ranks among the most acidic waters on Earth, with a pH level as low as 2—equivalent to the acidity of stomach acid. Its potent acidity is enough to kill any fish, and it would likely have the same fatal effect on humans who come into contact with it.
The acidic properties of Rio Tinto are a result of bacteria and iron that has leached into the water over centuries. Interestingly, similar conditions have been observed on Mars, leading some scientists to speculate that Rio Tinto might offer insights into the potential for life on the Red Planet. While this idea might sound far-fetched given the shared redness of both locations, there's no denying that, much like a grizzly bear, Rio Tinto is both stunning and dangerously off-limits.
9. Boiling Lake, Dominica
The name 'Boiling Lake' leaves little to the imagination: it's exactly what it sounds like. First discovered in 1870 by two English explorers, temperatures around the lake's edges reached between 82 and 91.5°C (180 to 197°F) five years later. That’s hot enough to burn skin, but those readings were just at the edges. The center of the lake is far hotter—so much so that it's impossible to get an accurate reading without risking your life.
The prevailing theory is that Boiling Lake sits above a pool of molten lava, with gases rising through the water, superheating it to extreme temperatures.
8. Lake Kivu, Border of DRC and Rwanda
Deep beneath the surface of Lake Kivu, around 300 meters (1,000 feet) down, lies a potential disaster waiting to happen. This lake contains more than 250 cubic kilometers (60 cubic miles) of carbon dioxide, as well as about 65 cubic kilometers (15 cubic miles) of methane gas. While this could generate enough energy to power multiple nations, it also holds the capacity to obliterate surrounding communities with a deadly flood of gas if disturbed. For now, these gases remain inert, but a volcanic eruption—something not uncommon in the region—could trigger their violent release, causing catastrophic devastation.
ContourGlobal, a company based in New York, has a plan to safely extract the methane from Lake Kivu and use it to fuel a local power plant. However, if their efforts go awry and they inadvertently stir up the dormant gases, the results could be deadly for everyone in the area.
7. Citarum River, West Java, Indonesia
This is a body of water that could harm us, but only because of our own actions. The Citarum River might just be the most polluted waterway on Earth. With over 500 factories lining its banks and no waste management or proper sanitation systems in place, the river is overwhelmed by trash and debris, to the point where the water is nearly invisible beneath the waste.
And yet, this is the main source of water for the region. Locals rely on it for drinking, bathing, and even cooking. In doing so, they gamble with their health and safety every day. Unfortunately, they have little choice in the matter. The situation is their reality now—so much so that the trash has accumulated thick enough that you could probably sleep on it.
6. The Rivers of Johannesburg, South Africa
Catching E. coli is already a terrible experience, but imagine swimming in it. That’s the harsh reality in some of Johannesburg's rivers, where the levels of E. coli bacteria are far beyond safe limits. In places like Cheetah Bridge, the water contains 240 times the amount considered safe, while more seemingly 'pristine' spots like Kaalspruit have 190 times the acceptable limit.
The situation doesn’t seem to be improving, with local authorities in full denial. However, when health experts warn that drinking certain waters could potentially be fatal, it might be a good idea to take those warnings seriously.
5. Blackwater River, Virginia, USA
While too much water may not seem like a direct threat, it can cause havoc. Just ask the residents of Blackwater River in Virginia, who’ve seen the river rise and flood more frequently in recent years. After decades of relative stability, Blackwater River has overflowed and inundated nearby towns six times in the past decade. No fatalities have been reported yet, but it’s only a matter of time unless action is taken to tame the river.
Unfortunately, no one really knows why the Blackwater River is flooding so frequently. Various theories have emerged, such as excessive asphalt along areas that should absorb water and the river's inability to drain properly due to ongoing roadwork. Whatever the cause, local residents are eager to solve the mystery so they don't have to keep fearing for their lives as the floods return repeatedly.
4. Tualatin River, Oregon, USA
If you're in Oregon, the Tualatin River is not the spot for a fun day of swimming with your dog. Nearly a dozen dogs die each year from exposure to toxic blue-green algae. This harmful bacteria grows rapidly, turning the water into a deceptively beautiful turquoise color. Those unfortunate enough to ingest the algae may suffer from mild symptoms like stomach issues, or in severe cases, experience paralysis and even death.
The local Clean Water Services have a temporary fix when algae levels spike: they bring in fresh water from other sources and pour it into the Tualatin River, hoping to break up the algae clusters and wash them away. However, this is only a short-term solution. Like a villain in a never-ending horror franchise, algae always finds a way to come back and wreak havoc.
3. Potomac River, Maryland–West Virginia Border, USA
While most people associate the Potomac with Washington, DC, the river has another, far more dangerous reputation: a killer. The stretch of water between Great Falls and Chain Bridge is known for its violent rapids and waterfalls that send anyone unlucky enough to fall in plummeting for nearly 1.5 kilometers (1 mile). To make matters worse, the strongest currents lurk beneath the surface, meaning once you're sucked under, you stay there.
On average, six people die each year in the Potomac, with many others risking their lives just by getting too close to its waters. The danger has become so severe that local authorities launched a campaign with an incredibly direct warning: 'If you enter the river, you will die.'
2. Belle Fourche River, Wyoming and South Dakota, USA
Belle Fourche may not be toxic, boiling, or radioactive, but it certainly packs a deadly punch, particularly in one dangerous stretch. Authorities around the Diversion Dam have been pushing to close this mile-long section to the public, especially after a series of fatal accidents. In 2010, a father, his young daughter, and their friend drowned when the violent rapids overturned their boat and trapped them underwater.
Several other near-fatal incidents have occurred over the years, all caused by the unpredictable and powerful rapids in this part of the river. Though it doesn’t make the headlines often, this small stretch of water has proven itself to be deadly, whether officially closed to the public or not.
(Photo: Walter Siegmund)
1. Lake Karachay, Western Russia
Much like a stunning supermodel concealing a deadly secret, Russia’s Lake Karachay looks breathtaking but is extraordinarily lethal. Without a doubt, it holds the title of the most radioactive body of water on Earth. Used as a nuclear waste dump until the 1990s, the lake’s toxicity was so extreme that simply standing near it for just an hour could expose you to 600 roentgen of radiation—far more than enough to kill most humans who would perish from 500 roentgen over five hours.
In an effort to combat the radiation, Russia has been dumping large amounts of concrete into the lake, hoping to trap the radiation and keep it from reaching the surface. The approach seems to be working, as tests of the water downstream have shown no signs of radiation. Perhaps in 500 years, our descendants will be able to safely throw a pool party there—but don’t hold your breath.
