Lake Karachay, Russia
Karachay, translated from the local tongue, means Black Water. Lake Karachay is considered the most polluted place on Earth. This once beautiful lake is located in central Russia, close to one of the country’s largest nuclear facilities, the Mayak Production Association.
Since 1951, the Soviets used the lake as a dumping ground for radioactive waste from Mayak. The lake isn’t large, but it is now deadly due to years of heavy radioactive dumping. In the 1990s, researchers ruled that standing on the shores of the lake for just one hour would deliver enough radiation to kill a human being.
From a radiological perspective, the lake was ruled the most polluted place on the planet and, for the last 45 years, has been completely off-limits to the public. Karachay and the neighbouring areas are also desolate, nearly completely uninhabited by any wildlife of any kind. The toxic lake ruined the surrounding locations, air, and water, but as well the health of the people who used to live in the area. Cancer cases increased by 21%, birth defects by 25% and leukemia by 41% (source: business insider).
Citarum River, Indonesia
Thinking about taking a refreshing dip in Indonesia's longest river? Think again. Java is a tropical paradise that beckons visitors keen to explore its beautiful lands. But Citarum's hazardous waters couldn't be in a worse condition.
This is a river considered the most polluted on the planet. This is not a place to practice your strokes. Some 20,000 tons of waste and 340,000 tons of waste water are dumped direct into the river every day, with 2,000 or so industrial sites responsible for wreaking environmental damage on a devastating scale.
Citarum is highly toxic and deadly, its waters rich in mercury, lead and arsenic, and presenting great dangers to human health. There are areas where you cannot even see the water for all the rubbish and dead animals that are floating on the surface. The world's dirtiest river is a depressing sight, one to avoid at all costs.
The Boiling Lake, Dominica
Dominica's Boiling Lake is a startling sight. Hot waters bubble, vapours hang in the air, whilst the curious struggle to keep a safe distance. Take our advice on this and don't get too close. Lose your footing here and it could prove to be fatal.
Located in Morne Trois Pitons National Park, not far from Roseau, the Boiling Lake is, in fact, a flooded fumarole, an opening in the Earth's crust that emits steam and gases from the molten lava below. Breathing in the gases can be dangerous, whilst entering the water is an obvious no-no, and this is no place to take a swim.
From time to time the water does cool, but don't be fooled. The temperature here can rise in rapid fashion and, with the grey-blue waters having been known to reach close to 200 degrees Fahrenheit, taking a dip could have dire consequences.
Jacob’s Well, Texas
Jacob's Well beckons on a hot summer's day, its cool waters drawing divers and swimmers alike. Located not far from Wimberley, it's a popular spot for those keen to freshen up and escape the baking Texan sun. Yet hidden dangers lurk not far beneath the shimmering surface, making this a perilous place to take a dip.
The clear spring waters bubbling up from Cypress Creek, this is a captivating sight, with a mouth 12 feet in diameter that is hard to resist. But Jacob's Well is deep, with a sheer vertical drop that plunges some 30 feet down, before its passages and tunnels angle away, reaching an average depth believed to be around 120 feet.
This makes it a popular place for curious cave divers, although the risks should not be underestimated. Lives have been lost here and, even for those experienced in exploring such places, to venture beneath the surface is a hazardous pursuit.
The Nile River, Africa
The Nile River in Africa is one of the world’s longest and most famous rivers. However, the Nile also has many dangers. For a start, around 4.5 million of pollutants flow into the river every year making the waters highly unsanitary which could harm any one who comes into contact.
There are also deadly snakes and spiders in the Nile, but the greatest threat comes from the lurking Nile crocodiles that patrol the muddy banks here. These fearsome predators are huge, with adult males growing up to 16 feet long and often weighing as much as 750kg.
The crocs here are also fast -- able to swim at speeds of up to 35 kilometres per hour in pursuit of their unfortunate prey. Once you're in their sights, the chances are you won't get away. Thinking about swimming in the Nile? Think again.
Hanakapiai Beach, Kauai
Hanakapiai Beach is beautiful. Far from the beaten track, with no vehicular access, a significant trek is required to reach its golden sands. Remote and scenic, this is Hawaii at its spectacular best. Lie back and soak up the sun -- but don't think about going in the water.
The ocean here is perilous, with powerful waves, strong rip currents and dangerous shore breaks that have claimed countless lives. The official line is that around 30 people have drowned here since 1970. Yet the grim warning sign that greets visitors puts that number far higher.
Regardless, there can be no question that to swim here is to take a huge risk, with the immense currents sweeping the unprepared far out to sea without any warning, and the bodies of innumerable drowning victims never recovered. This might look like the perfect place to swim, but please heed the warnings and don't be foolish.
Bubbly Creek, Chicago
It sounds rather quaint and charming, and like the perfect spot to take a dip. Yet Bubbly Creek is no place for swimming. Its fetid waters have been cleaned up in recent times, but such is the filth that underpins this grim river, you still shouldn't think about venturing in.
The South Fork of the South Branch of the Chicago River, this was once an open sewer -- close to the city's great meatpacking district -- where blood and entrails from the surrounding slaughterhouses were once dumped in vast quantities.
It was the gases that bubbled up from the decomposing animal remains that gave the waterway its name. Not so quaint and charming after all. Huge 'sludge-bergs' made from grease and chemicals once blocked the river, whilst methane and hydrogen sulfide made the smell unbearable. The perfect spot to take a dip? Don't even think about it.
Samaesan Hole, Thailand
Located in the Gulf of Thailand, the Samaesan Hole is one of the world’s most dangerous and deepest dive sites. The bottom is almost 300 feet beneath the surface. The risks don't end there. Thinking about exploring the mysterious depths? There are countless challenges to overcome in these hazardous waters.
For one thing, this is a busy shipping lane, with huge oil tankers amongst the traffic passing through these parts. For another, the currents are strong, with divers often surfacing miles from the dive site's entrance. Some are rescued by passing ships, but not all are so fortunate.
Then there's the fact that this was once an off-limits military dumping ground, where hazardous waste and explosive devices were cast aside. With the tankers on the surface, unexploded bombs below, and a powerful current present throughout, to swim here is a risk too great to take.
Eagle’s Nest Sink Hole, Florida
On the surface, Eagle's Nest looks like just another pond in Florida's tropical swamp lands. Down below, however, a captivating underwater world awaits. There's a great tubular chimney, vast caverns and passages galore that beckon the adventurous.
The problem is, it's dangerous down here. Since 1981, at least 10 experienced divers have drowned at Eagle's Nest, prompting authorities to call for a ban on entering these perilous waters. Located in the remote Chassahowitzka Wildlife Management area, Eagle's Nest remains a huge draw, despite the risks, with divers determined to make it all the way to the sink hole's famed Super Room.
Yet the dangers are great, with poor visibility, and issues surrounding guidelines and gas supplies always posing a threat. The underwater tunnels here drop at least 300 feet beneath the unremarkable surface. Few have ever explored them in depth and lived to tell the tale.
Kipu Falls, East Kauai
Image: Bryce Edwards, Wikimedia Commons
You might recognise Kipu Falls from Raiders of the Lost Ark. However, those aspiring to be Indiana Jones should not be tempted to visit. For one thing, this is private property, with trespassing prohibited.
For another, it's a dangerous place, where drowning is commonplace, with many of those who choose to ignore the warnings paying the ultimate price.
Located in East Kauai, this is a spectacular place, but the waterfall and swimming hole that beckon adventurers hide dangers that cannot be seen from the surface. Those who do venture in are often dragged down to the depths and drowned.
Some believe that this is due to the presence of an angry mo'o, a Hawaiian spirit lizard, although the more prosaic explanation is a powerful whirlpool that generates immense underwater currents. Whatever the reason, this is one to avoid -- with swimming here a risk that is just not worth taking.
The Amazon Basin, South America
There's no shortage of water in the immense Amazon Basin. Swimming here, however, is not recommended. The dangers are countless. The mighty Amazon is regarded as the deadliest river on Earth and such a reputation is warranted.
Its brown waters are becoming increasingly polluted, with toxins from mining and other industries being dumped here. That isn't the greatest threat, however. Natural dangers trump those man-made, with strong currents and fearsome creatures posing significant risks for anyone thinking about venturing in. You've heard about the piranhas, but arapaima -- a huge carnivorous fish -- can be even deadlier.
Not dangerous enough yet? What about the anacondas, leeches, electric eels, highly poisonous frogs and giant tarantulas that all make their homes here? Then it's clear that this is no place to take a dip. With parasites present and danger at every turn, we recommend finding somewhere else to practice your river swimming.
Lake Victoria, Africa
Lake Victoria is vast, spanning 70,000-square kilometres, its banks straddling three different countries -- Uganda, Kenya and Tanzania. It's also deadly. With around 5,000 people thought to perish in its waters each year, it is regarded as the most dangerous lake on the planet.
It might look tranquil, but think twice about taking a dip here. Countless swimmers underestimate Lake Victoria, and many pay the ultimate price. The problem here is the weather, which is unpredictable, erratic and prone to sudden change. The conditions might appear perfect, but the lake has its own micro-climate and the weather can deteriorate without warning.
Torrential rain, thunderstorms and freak waves are always a danger. Even on a boat, you're far from safe, with innumerable fishermen drowning here on a regular basis, their vessels capsized and their efforts to stay afloat sadly in vain. The survival statistics here make for grim reading. Take our advice and don't become part of them.
Horseshoe Lake, California
Horseshoe Lake enjoys a stunning location, its waters shimmering in the Californian sun, with swaying trees and mountains all around. Yet first impressions can be deceptive.
Set high in the hills, in Lassen Volcanic National Park, not far from the Mammoth Mountain Ski Resort, this is a place fraught with danger -- where swimming is permitted, but best avoided.
The problem here is gas -- carbon dioxide, in particular. Issues first arose in 1989 and 1990, when a series of small earthquakes in the region opened cracks and crevices that allowed dangerous gases from the bubbling magma below to rise to the surface. The result? Polluted soil -- and more than 100 acres of dead plants and trees.
These days, nothing grows in the affected areas and, with gases and toxins from the banks leaching into the lake, the dangers here endure. Thinking about paying a visit? Be sure to look out for signs, and always heed warnings.
Rio Tinto, Spain
Spain's bright red Rio Tinto is a spectacular sight as it flows from the Sierra Morena mountains -- colouring the surrounding landscape as it passes. Visitors are drawn here to see its eye-catching colours, but those thinking about swimming in the vibrant waters should think again.
The Rio Tinto is extremely acidic, with a pH as low as 1.7, so a dip here would be hazardous! The Rio Tinto's chemical nature is the result of extreme mining pollution, with heavy metals -- including gold, silver and copper -- present in the water in significant proportions. The result is a harsh environment that isn't conducive to life.
There isn't much living here, and those venturing in will be putting their health at risk. Dangerous bacteria thrives under such conditions and, whilst the river can be pleasant to look at, bathing should be avoided. Do take a look, but don't take a dip.
The Ganges River, India
The Ganges is a sacred place. Local people have long believed that to bathe in its waters is to be cleansed from all sin. Taking a dip here is not uncommon. But those thinking about swimming in the river are taking a great risk.
It might be renowned for cleansing sins, but the truth is that India's great waterway is polluted and dirty. Some 300 million litres of untreated domestic sewage are emptied into the river each day, whilst industrial waste and the corpses of those whose impoverished families are unable to afford a funeral are also dumped in the murky depths.
The result is a breeding ground for illness and disease and, whilst local people continue to bathe here, hepatitis, dysentery, typhoid and cholera are amongst the risks posed. It might be a sacred place, but the Ganges is hazardous to health and best avoided at all costs.
Gansbaai, South Africa
Image: Olga Ernst, Wikimedia Commons
Gansbaai's beaches are beautiful, the sands golden and the waters warm. The shore is tree-lined and the sun always shining. But beneath the shimmering waves, all is not as it appears. This might look like paradise, but danger always lurks and those who enter the ocean are at risk.
Located on South Africa's southern coast, not far from Cape Town, the waters here are home to the densest population of Great White Sharks on Earth. Drawn to 'shark alley', a small channel between Dyer Island and Geyser Rock, where fur seals are abundant, the great predators are getting ever closer to the scenic shoreline.
Planning a visit? Look out for warning signs and always take heed. For those keen to see the sharks up close and personal, tours are available, with divers lowered into underwater cages. This is a safer option than swimming -- but the best bet of all is to stick to the sand and give the ocean a miss.
Hoover Dam, Nevada
The deep reservoir that stands atop the imposing Hoover Dam is some 660 feet from one side to the other. Until 2017, no-one who attempted to swim across had ever lived to tell the tale.
This is an undertaking that is fraught with danger. Thinking about taking it on? You'll either end up in a police cell or a coffin.
In the ten-year period leading up to 2017, 275 people are known to have died here, on the Nevada-Arizona border. That a drunk British man managed to make it across that year was fortunate, his survival put down to the fact that nine of the dam's 10 great hydroelectric turbines were not operational that day.
Had the Hoover Dam been working to full capacity, the chances are he would have been dragged beneath the surface and drowned, like so many before him. Still thinking about taking it on? The chances are you won't be so lucky.
Blue Lagoon, UK
The Blue Lagoon sounds lovely. Its shimmering waters are turquoise and appealing -- beckoning those keen to cool down on a hot summer's day. The trouble is, those appealing waters are also harmful to health. It has been described as a 'toxic soup'. Trust us on this one: swimming here is not a good idea.
Located close to Buxton in Derbyshire, this is a former quarry, the waters containing dangerous residues that point to its industrial past. High in calcium oxide, the Blue Lagoon has a pH of 11.3. In comparison, ammonia is 11.5 and bleach 12.6.
Consider that, down the years, this has become a dumping ground, with abandoned cars, rubbish and rotting animal carcasses all hidden in the depths, and it starts to sound a little less lovely. The authorities here have even tried dying the water black -- in order to make the 'lagoon' less attractive -- yet still people swim here, forever risking illness and injury.
The Gulf Coast, United States
The Gulf Coast's warm waters shimmer in the sun, beckoning those keen to cool off. Swimming here is not recommended, though. It might look a lot like paradise, but danger lurks beneath the gentle waves, and the risks here are significant.
Countless creatures favour the Gulf Coast conditions and not all are willing to share the water. Look out for sea snakes, stingrays and jellyfish. Not far from the shores, sharks are always on the prowl. Still willing to accept the risks? Be aware that the rip currents here can take the unsuspecting out to the deeps, where even greater dangers can be found.
Reports of a flesh-eating bacteria that is rampant out here should be sufficient to prompt a rethink. There are some great places to swim in the United States -- but this is not one of them.
Reunion Island is a popular spot for those seeking paradise -- a beautiful French resort in the Indian Ocean, where the sun always shines, the sands are golden and the waters warm, it's a great place to hike, surf and dive - as you can see whales, dolphins and beautiful exotic fish. However, great dangers lurk in those waters and you don't want to go in the water without a guide.
There has been a sharp rise in shark attacks here in recent times, many of them fatal. This is considered a high-risk location -- with surfers in particular danger. Dubbing the issue 'the shark crisis', island authorities have banned surfing in certain areas, yet still people take their lives in their hands and head out on their boards, never guaranteed to return.
Reunion lies on the so-called 'shark highway', between Australia and South Africa, hence the increasing number of deadly predators here. Between 2011 and 2016, 16% of the world's fatal shark attacks happened in Reunion's waters. Still thinking about swimming?
The Strid, England
Quintessentially-English, the River Wharfe tempts those keen to cool off on a hot summer's day. It's a scenic spot, with its tree-lined banks and moss-covered rocks. But don't be fooled. This Yorkshire paradise is a perilous place, where countless people have perished.
Local legend has it that no-one who has set foot in the waters here has lived to tell the tale. There are warning signs all around, yet still the curious come. The Strid is the most dangerous section. The river here narrows dramatically, but whilst all appears calm on the surface, deep and powerful currents rage below, dragging those foolish enough to venture in down to the underwater voids that have claimed so many lives.
The hollowed out rocks here can trap swimmers, with fatal consequences, the water deep and cold, and the forces immense. Take our advice on this one: don't be fooled and don't even think about swimming here.
Image: John Robert McPherson, Wikimedia Commons
There are countless reasons not to swim in the warm waters that lap Queensland's scenic shores. Dangerous creatures abound here. Taking a dip? You're taking a risk. Stick to manned beaches, look out for flags and warning signs and always listen to the lifeguards. Taking such precautions can mitigate the dangers. Yet still this is a hazardous undertaking.
Crocodiles can often be found lurking here -- both in fresh and salt waters -- whilst sharks patrol the coastline, always on the hunt for their next meal. The greatest danger, however, comes from the jellyfish, with box jellyfish and the highly-venomous Irukandji a constant threat.
Been stung? Seek medical attention at once. With poisonous octopuses, stonefish, stingrays and sea snakes amongst the other dangerous creatures that call the oceans here home, it might be best to avoid a swim altogether and make the most of the sands instead.
Bolinas Beach, California
Big Sur -- a rugged stretch of central Californian coastline -- beckons beach lovers with its pristine sands and sparkling waters. The ocean here teems with life, an area known as the Red Triangle (stretching between San Francisco, the Farallon Islands and Monterey) renowned for its thriving marine habitats.
Innumerable fish and playful seals are amongst the creatures that call this area home. But with so much life in the water, sharks are never far away. Bolinas Beach is popular with surfers, yet with great whites amongst the shark species that patrol the scenic shores here, going into the water is always a perilous pursuit.
Shark bites are not uncommon, with figures suggesting that 11% of worldwide shark attacks occur in the ocean around this point, with those venturing too close to the Red Triangle in particular danger. Still thinking about taking a dip? It might be best to stick to the sands.
New Smyrna Beach, Florida
New Smyrna Beach is popular with surfers and tourists. The trouble is, it's also popular with sharks. In recent times, it has gained a reputation as the 'shark attack capital' of the world. To venture into the warm waters here is to risk being bitten -- or worse.
Numerous species have been spotted here -- including great whites -- and scientists estimate that anyone who has ever swam at New Smyrna has been within 10 feet of a shark. It's a frightening thought, yet so good are the conditions here, surfers continue to come in numbers, taking their lives in their hands each time they enter the shimmering Florida waters.
Located just south of Daytona Beach, the sands are beautiful here and the climate perfect. But with Volusia County leading the world in recorded shark bites for several years now, you might want to think twice about taking a dip.
Victoria Falls, Zambia
It is often described as the ultimate infinity pool. It's a perilous place, for sure, yet still thrill-seekers take their lives in their hands and head here, to bathe atop the largest waterfall on Earth.
Located close to the border between Zambia and Zimbabwe, Victoria Falls is a spectacular sight, the powerful Zambeze River plunging 100 metres down onto the rocks below, its currents strong and the drop great. Some 500 million litres of water cascade over the falls every minute. Yet it's possible to get right to the edge, at Devil's Pool, where a rock lip prevents adventurers from being swept away -- in theory, at least.
The falls are twice the height of Niagara and although guides are on hand to reduce the risks, there's no question that this is a hazardous pursuit. The fact that crocodiles and hippos are often found in the wild waters here just adds to the danger.
Potomac River, United States
There are various reasons not to take a dip in the Potomac River -- not least that swimming in certain sections is illegal under US law and likely to land you in trouble with the authorities here.
The legalities aside, swimming just isn't safe here. With the hazards ranging from white water rapids to deadly bacteria and overflowing sewage pipes, our recommendation would be to seek somewhere else to practice your strokes.
It can be tempting to take the chance in Maryland's Great Falls area -- aka Mather Gorge -- but don't be fooled by the beautiful surroundings.
This is a dangerous spot, with strong currents, deep waters and hidden hazards that result in frequent drownings. Closer to Washington DC, high E.coli readings continue to cause concerns, whilst flash floods often result in sewage being dumped into the river. One to avoid? For sure.
West End, Bahamas
Tourists flock to the beautiful Bahamas to take a dip alongside the famous swimming pigs. But venture into the waters off West End and you could find yourself face-to-face with creatures that are rather more dangerous.
Located on Grand Bahama, this is the island's oldest town and western-most settlement. It's also home to countless sharks, with the infested waters here considered amongst the most dangerous on Earth.
Tiger Beach is named after the tiger sharks that patrol its pristine shores. Make no mistake, this is a dangerous beast, second only to the great white shark in its fearsome reputation, and known to grow up to 16 feet long here. Shark tours are offered to the courageous -- or foolish -- but we recommend remaining on the boat and taking a much-safer fishing trip in search of the tuna and marlin that live a little further out.
Lake Kivu, Rwanda
Located close to the beautiful border between Rwanda and the Democratic Republic of Congo, Lake Kivu is a spectacular sight. Its shores are tree-lined and mountainous, its waters emerald green, shimmering in the warm sun.
But all is not as it seems beneath the surface of Africa's sixth largest lake. People do swim here, but most come to regret it.
The water looks lovely, but its rare chemistry makes it hazardous to health. There are large concentrations of methane and carbon dioxide here, the deadly gases often bubbling up from the volcanic bottom in what local people call a 'mazuku', or an evil wind.
Being poisoned is always a possibility, whilst with dangerous microorganisms lurking in the lake, picking up a nasty illness is also a significant risk. Factor in the parasites that are at home here and you should reach the conclusion that swimming isn't a good idea. Go and take a look at the lake, but don't be tempted to venture in.
Myrtle Beach, South Carolina
With its long boardwalk, famous Ferris wheel and perfect climate, Myrtle Beach is a tourist hotspot. This South Carolina vacation resort is popular with families, bound for the sands and the inviting Atlantic Ocean.
The problem is that countless sharks patrol the waters here, coming ever closer to shore and making swimming perilous. Ever seen Jaws? You get the idea.
The truth is that attacks are uncommon, but with some 40 shark species -- including blacktip sharks, bull sharks and tiger sharks -- all at home here, taking a dip does involve certain dangers.
Can't resist? Be sure to avoid swimming at dawn and dusk, steer clear of the piers and known shark hotspots, try to move gracefully in the water and stay in a group, and above all, always heed the warnings. Sharks have been photographed lurking incredibly close to unsuspecting swimmers here. Be aware and be prepared.
Gulf of Thailand
The Gulf Of Thailand is a beautiful shallow inlet in the warm South China Sea, boxed in by Thailand, Vietnam, and Cambodia, and beckoning visitors with its pristine beaches and lush tree-lined shores.
Taking a dip here is tempting, we get it. But before taking the plunge, do consider the dangers, and be aware that all is not as safe as it might at first seem.
Thailand's gorgeous gulf is home to some serious species, with sea snakes, lionfish, stonefish and jellyfish amongst the creatures lurking in its shimmering waters.
Of these, it is the jellyfish that perhaps pose the greatest danger, and for those who fear a painful -- or poisonous -- sting, staying out of the water is the best bet. Feeling brave? Be aware that rip currents are common here, and that most beaches do not have a lifeguard. Look out for red warning flags and always use your common sense.
Blue Lake, Russia
Russia's Blue Lake is beautiful. It's also dangerous for various reasons. For one thing, the waters here are cold, making hypothermia a constant hazard. For another, it's deep -- plunging at least 846 feet down beneath the surface, making it one of the deepest lakes on Earth.
It's a mysterious place, fed by no rivers or streams, its underwater source unknown. There is thought to be a huge unexplored cave network deep beneath the surface, making it appealing to divers, although even the most experienced are at risk in the depths, and deaths here are not uncommon.
The waters here are crystal clear, although the smell is off-putting -- the high levels of hydrogen sulfide found in the water prompting some local people to call this 'Stinky Lake'. Enjoy the spectacular scenery, with gorgeous tree-lined hills all around, but remember that to swim in Blue Lake's frigid waters is to take a significant risk -- regardless of your ability.
Mono Lake, California
Mono Lake is a strange place. Located in the arid Great Basin, it's an oasis, covering 70 square miles and providing a vital habitat for birds. Beneath the surface, however, life is limited.
No fish swim in Mono Lake's saline waters, although trillions of brine shrimp have made this their home. The reason? Mono Lake is super salty. Boasting a pH of 10, the waters here are said to be three times saltier than California's neighbouring oceans.
Enjoying a spectacular location -- with the beautiful Sierra Nevada mountain range providing a beautiful backdrop -- Mono Lake is ancient, dating back at least 760,000 years (and thought to be as old as three million years). People have long headed here to take a look and it remains a popular destination on the tourist trail. Like to get up close and personal? Take our advice: keep your feet dry, and choose a canoe tour.
Laguna Caliente, Costa Rica
Located high up on Poas, an active volcano in Central Costa Rica, Laguna Caliente's bright blue waters are a spectacular sight. Do come here and take a look. Don't be tempted to take a dip.
This is a crater lake hazardous to health, its waters amongst the most acidic on Earth, where little or no aquatic life is found, and those who get too close are exposing themselves to significant dangers.
The acid gases that rise up from the lake can irritate eyes and lungs, whilst there's always the chance that Poas could explode. There have been 40 eruptions here since 1828 -- the last in 2017, when visitors had to be evacuated and the National Park closed for almost 18 months. Despite the dangers, Laguna Caliente calls to the curious. Can't keep away? That's fine -- but remain a safe distance and don't even think about swimming here.
The Atomic Lake (Lake Chagan), Kazakhstan
Lake Chagan is a man-made lake in Kazakhstan. It was created in 1965. Using a nuclear bomb. Thinking about taking a dip in its peaceful-looking waters? Take our advice and think again. Lake Chagan isn't known as 'Atomic Lake' for nothing.
Decades have passed but the radiation remains and there can be no question that this is a lake hazardous to health. The surrounding landscape is bleak and life here scarce.
It's perhaps no surprise given that, in the 1960s -- the Cold War at its height -- the Soviets used this as the location for a nuclear test, detonating a 140-kiloton device, placed in a 178-metre deep hole in the dry bed of the Chagan River. The result was predictably devastating and, all this time later, the effects are still being felt. The waters here will be radioactive for years to come and those planning to swim in 'Atomic Lake' would be foolish.
Lake Nyos, Cameroon
Locally, Lake Nyos is known as the Bad Lake. Even for those not planning to take a dip in its perilous waters, it poses great danger. One to avoid? We recommend giving this place a wide berth.
Located high on an inactive volcano, this is a crater lake like no other, a magma pocket deep beneath the surface leaking carbon dioxide into its waters, making carbonic acid in the process and threatening all around. The natural wall that forms the lake's perimeter is starting to crumble, threatening countless villages that lie beneath. Yet it is not Nyos' acidic waters that pose the greatest threat to life here.
In 1986, natural disaster struck, a huge explosion sending a fountain of water 300 feet into the air. In the process, deadly gases were released, poisoning those who breathed them in -- and killing more than 1,700 people. One to avoid? This isn't called the Bad Lake for nothing.
Thinking about taking a dip? Nyiragongo is not the place. The setting is spectacular, for sure, a scenic location like no other. But make no mistake -- those are not warm waters, but the largest lava lake on Earth.
The heat here is such that you'd be hard pressed not to notice, the super-fluid lava forever bubbling and, from time to time, spilling out and consuming everything in its path.
Located deep in the impenetrable Democratic Republic of Congo, this is a volcano known for its volatility. Eruptions are not uncommon here. Taking a trip? You're taking a chance.
Travelling to Nyiragongo requires a significant trek through thick jungle, yet visitors are drawn to the captivating crater -- measuring 1.2km in diameter -- that houses the deep lava lake. By all means, make the climb and take a closer look. But leave the trunks and towel at home.
Berkeley Pit, Montana
Swimming here is an absolute no-no. Berkeley's acidic waters are deadly, a poisonous mixture of dangerous chemicals and harmful heavy metals. The 4,000 or so unfortunate snow geese who landed here in 2016 did not live to tell the tale. Please avoid this at all costs or risk suffering the same fate.
It's a strange place -- a toxic waste dump that is also a tourist attraction -- but people do come here to visit. The former open pit copper mine, located just outside Butte, Montana, is one mile long and half-a-mile wide, with deep waters that go down 900 feet.
Those waters contain various harmful substances -- including arsenic -- and are said to be as acidic as cola, vinegar and lemon juice. Anyone foolish enough to drink from the lake would suffer a painful end, their digestive system being corroded from the inside. Taking everything into consideration, this is one to avoid.
Beqa Lagoon, Fiji
In Beaa Lagoon, eight species of shark prowl and danger is always present. Local people have been swimming with predators here for more than 3,000 years, worshipping the shark god, Dukuwaqa, in order to avoid being attacked. Thinking about taking a dip? Be sure to say your prayers first.
Make no mistake about it: with tiger sharks and bull sharks amongst the species patrolling the waters around Viti Levu, swimming here is a hazardous undertaking. Like to reduce the risks?
Be sure to engage the local shark wranglers, who will distract the sharks with food whilst you watch from behind an underwater wall. To see sharks up close and personal like this is an amazing experience. But such fearsome creatures can be unpredictable, and if things were to go wrong, the consequences could be dire.
Pustoye Lake, Siberia
Located in Western Siberia, picturesque Pustoye Lake looks pleasant enough. That 'pustoye' means 'empty' in the local tongue tells a different story, however.
This is a lake where nothing lives -- and no-one knows why. Countless studies have been done here, but answers remain elusive. Scientific tests suggest that the water here is harmless, but no fish live in the lake and, with no plant life or other organisms present either, it remains a mysterious place.
Siberia's Altai territory is a place of innumerable lakes and waterways, a land teeming with life, where natural wonders abound and trees dot the scenic hillsides. This just adds to the riddle, with Pustoye's shimmering surface hiding secrets that none have been able to uncover. There's nothing official to suggest that swimming here could be harmful to human health. That said, given the mysteries that endure, we'd recommend giving this a wide berth.