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Here are a few places where you should only swim at your own risk — and probably not even then.
Any body of water can be scary, depending on how you look at it. Drowning is always a possibility and who knows what might be lurking underwater.

That said, there are some lakes that are pretty objectively terrifying. Whether it’s because of the things living in them, the bizarre geology of the area they’re in, or the seemingly random things sitting under the surface, you really don’t want to go for a dip in them.

Here are seven of the most horrifying lakes from all around the world.

1. Lake Nicaragua — The Shark Lake
Lake Nicaragua, unsurprisingly located in Nicaragua, is a beautiful tropical body of water. It’s the largest lake in Central America, but there’s another thing that makes it even more unique.

There are sharks in it.

Despite Lake Nicaragua being filled with fresh water, sharks are living in it (alongside some other fish usually found in salty waters). For the longest time, researchers assumed the sharks were a unique species stranded in the lake during some ancient cataclysm.

Later, however, it was revealed that the sharks are actually marine bull sharks. As it turns out, the fish can jump up the rapids of the San Juan River like salmon until they reach the lake.

Bull sharks are also one of the most common shark species to attack humans. Care to go for a swim?

2. Roopkund — The Skeleton Lake
Roopkund is a glacial lake high up in the Indian Himalayas. For most of the year, it’s fairly unassuming, lying frozen under a thick layer of snow.

But once spring comes and the snow melts, Roopkund reveals its gruesome secret. Around the lake’s shore, just below the surface, lay scattered hundreds upon hundreds of human skeletons.

No one knows how exactly the remains ended up in the lake. Tests have shown that the unfortunate people died in at least two catastrophic events, some as early as 1,200 years ago.

The skeletons are visible for only one month each year. Afterward, the quickly arriving Himalayan winter buries them again in their icy grave.

3. Lake Nyos — A Ticking Gas Bomb
Lake Nyos is a crater lake in northwestern Cameroon. It’s also a gas bomb that has claimed nearly 2,000 lives.

Underneath the lake sits a pocket of magma, which constantly pumps carbon dioxide into the water. In 1986, Nyos erupted, belching out an enormous cloud of CO2 that suffocated all life around it, including nearly 1,750 people and 3,500 farm animals.

As CO2 began building up in the lake again, pipes were installed to drain the gas and (hopefully) prevent such a disaster from repeating. But a new threat has since reared its ugly head — the natural dam keeping the lake waters in place has begun weakening dramatically.

Curiously, Lake Nyos is only one of the world’s three exploding lakes. The other two are lakes Monoun and Kivu, which are also in Africa.

4. Lake Karachay — World’s Most Radioactive Lake
Lake Karachay in Russia no longer exists — and that’s for the better. That’s because during its life, it was the most radioactive open-air location in the world.

It’s all thanks to the nearby (still active) Soviet-era nuclear weapons facility that used the lake as a dumping ground for radioactive waste. At its peak, the lake’s radioactivity was comparable to Chornobyl during its famous meltdown.

To put that into perspective, sitting just an hour at the lake’s shore would be a guaranteed death sentence.

Lake Karachay was finally filled between 2015 and 2016 and the levels of radioactivity have started dropping. But that wasn’t before the lake began drying up, sending radiating dust blowing off with the wind.

5. Lake Natron — A Salty Death Trap
As soon as you see Lake Natron, you know something bizarre is going on. That’s because it’s partially red.

The color is due to cyanobacteria that live in the lake’s incredibly salty and alkaline waters. And they’re pretty much the only things that can live in it, barring the flamingos that flock to Lake Natron’s shores.

Few animals venture into the waters because of their high heat and extreme salinity. If they do, though, they will soon die.

And, because of the high salt content, the animals’ remains will quickly mummify. Dried carcasses of hapless birds and other animals litter the lake’s shores, their foolishness preserved for ages to come.

6. The Boiling Lake — Exactly What It Sounds Like
The Boiling Lake is a flooded volcanic vent on the Caribbean island of Dominica. It’s called that because it’s… Well, boiling.

The Boiling Lake’s waters are in constant contact with an open magma vent on its bottom. As a result, it’s constantly in a rolling boil, filling the air around with steam and the stench of sulfur.

You’d imagine the lake would eventually boil dry, but it’s constantly fed enough water that it never does. The water level does fluctuate wildly and it sometimes gets nearly empty, just to fill up again within 24 hours.

7. Laguna Caliente — A Literal Acid Trip
Laguna Caliente (Spanish for “hot lagoon”) is one of two crater lakes at the summit of Poas Volcano in Costa Rica. It has the dubious honor of being the most acidic lake in the world.

Like the Boiling Lake, Laguna Caliente sits right on top of a volcanic vent. Although the water is warm, it doesn’t boil — but the volcanic contact turns the water extremely acidic.

The lake’s pH hovers right around zero, making it comparable to battery acid. In fact, its bottom is covered in a layer of liquid sulfur.

The acidic gases and fog emanating from the lake make its surroundings inhospitable, as sticking around would quickly begin to burn your eyes and lungs. Yet, life always finds a way — there is one type of bacteria that has a grand old time in the lake’s otherwise fatal waters.