There are more than 100 million lakes in the world, covering almost 4 per cent of the planet’s surface. For the most part they are bustling biodiverse hubs of life, providing habitats and resources for billions of living things, but some lakes have a dark side.
From lakes that explode to lakes so acidic they burn, here are ten of the world’s deadliest lakes.
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Deadliest lakes in the world
Lake Karachay
This small, dusty lake, in Russia’s southern Ural Mountains, is, hands down, the world’sdeadliest lake. Before 1951, Lake Karachay was unremarkable. Invertebrates hummed. Fish swam . Birds fished. But then the Soviet Union began dumping radioactive waste in it, from a nearby nuclear processing facility.
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The Mayak plant, as it was known, was part of a secret mission to produce plutonium for the Soviet Atomic Bomb Project and the dumping continued until 1957, when a nuclear accidentat the plant put an end to it.
Much too little. Much too late. By this time, the lake had amassed large amounts of radioactive isotopes, including caesium-137 and strontium-90, with a total radioactivity exceeding that released by the Chernobyl disaster.
Then things got even worse. The lake started to dry up. In 1968, the wind blew a cloud of radioactive dust away from the lake which irradiated half a million people. After that, the lake was infilled with concrete blocks and rubble, creating a permanent dry nuclear waste storage facility, that was completed in 2016.
The lake’s legacy, however, persists. Radiation levels remain so high they can deliver a lethal dose to a person in less than an hour, making this one lake that no one should ever visit.
Lake Nyos
For years, it was a ticking time bomb. Lake Nyos is located in a volcanic region in northwest Cameroon. There, carbon dioxide released from underground magma seeps up through the ground and into the lake, where it dissolves in the deep still waters. Over time, the amount of carbon dioxide just builds and builds, until eventually, it explodes.
This happened on August 21st, 1986, when around 200,000 tons of carbon dioxide was released from the bottom of the lake into the atmosphere in one enormous, life-snuffing explosion. The gas cloud initially rose at nearly 100 kilometres per hour, and because carbon dioxide is heavier than regular air, it then rolled down the hillside and engulfed the nearby villages. Around 1,700 people and 3,500 livestock were asphyxiated.
Known as a limnic eruption, this was not the first time the phenomenon had happened. A similar event two years earlier, at nearby Lake Monoun, killed 37 people. Now both lakes are fitted with degassing pipes, which are designed to shuttle dissolved carbon dioxide away from the depths and make future limnic eruptions less likely.
Lake Victoria
At nearly 70,000 square kilometres, Lake Victoria is Africa’s largest freshwater lake, home to perch, tilapia and the native Lake Victoria sardine. More than 200,000 people fish on the lake, supporting the livelihoods of millions more, but these are dangerous waters. Every year, up to 1,500 fishers drown. Most of them are men. Most are under 40, and most die when they take their small boats out in bad weather.
Researchers have found a number of reasons for why this is. Very often the fishermen are the family breadwinners. They feel forced to go out, even when the weather is bad, because they need to provide for their family. Decades of overfishing mean that stocks of Nile perch, which are fished during the day, have declined. So, instead they go after sardines, which are fished at night, when the weather tends to be worse. And although their boats are generally in good shape, the men rarely have life jackets or the navigation equipment that they need to get themselves out of trouble.
It’s a sad and desperate situation. As the global climate continues to change, bad weather is likely to become more common on the lake. Now action is needed to prevent these all too avoidable tragedies.
Lake Kivu
Lake Kivu is one of the African Great Lakes. Situated on the Rwanda-Congo border, it is one of a handful of lakes known to contain dangerous levels of harmful gasses dissolved in their lower layers. When an earthquake or volcanic activity causes the gas to be dislodged and rise to the surface, it kills people. ‘Limnic eruptions’ at Lakes Nyos and Manoun, both in Cameroon, back in the eighties, killed 1,746 and 37 people respectively.
Scientists estimate that Lake Kivu contains 300 times more gas than Lake Nyos did before its fatal eruption, and that the lake has been killing regularly on a roughly 1000 year cycle. Geologists found evidence of massive local extinctions occurring on this time scale, which they think were caused by limnic eruptions.
Levels of the dissolved greenhouse gases are now becoming dangerously high, and it’s thought the next eruption could occur within the next century or two. With around 2 million people living on Lake Kivu’s shoreline, the repercussions of this could be devastating. And whilst projects are underway to extract methane from the lake, only time will tell if they are enough to avert a future tragedy.
Horseshoe Lake
Trees are meant to love carbon dioxide. They absorb it from the air and along with water, they use it make glucose and oxygen. Thanks, photosynthesis, for giving us the air we breathe. Things aren’t so peachy, however, when there are high levels of carbon dioxide in the soil.
This is the case for a 120-acre area on the banks of Horseshoe Lake, on the south side of Mammoth Mountain, California. Here, magma beneath the ground releases carbon dioxide, which seeps up into the soil, where it reaches levels of up to 90%. This alters the pH of the soil, creates an oxygen poor environment, and makes it difficult for tree roots to respire and absorb the nutrients they need.
As a result, the northern bank of Lake Horseshoe has areas of ‘ghost forest’ where there are dead trees that have essentially been suffocated to death.
Lake Natron
In recent years, Lake Natron found fame when photos of animals, supposedly turned to stone by its caustic waters, began circulating on social media. The truth, however, is a little less Greek mythology, and a little more school chemistry.
Lake Natron contains high levels of a naturally occurring mineral called natron, which is a mixture of soda ash and other salts. It also has no natural outlet, and is situated in northern Tanzania, where it is very hot. As the water evaporates, the minerals become more concentrated, which makes the remaining water increasingly alkaline. At times, its pH can reach 12, which is the same as household bleach.
Flamingos and other species that are adapted to living there can tolerate this, but most species cannot. A brief dip in the water is enough to cause skin irritation and burns, and if an animal dies near the lake and then stews in its juices, it can become mummified. This is what lead to the macabre, bleached corpses of the animals that were photographed.
Lake Okeechobee
Covering 1,900 km2, Lake Okeechobee is the largest freshwater lake in Florida. From bass to snakes, manatees to turtles, the water is teeming with wildlife, including around 30,000 alligators who call the shallow lake their home. This makes Lake Okeechobee the most alligator-infested water in Florida.
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American alligators, which can grow up to 4.5 metres long, are not fussy eaters. In Lake Okeechobee they eat anything they can sink their teeth into, including turtles, snakes, small mammals and birds. Human casualties are rare, but not unheard of. In 2025, a woman was killed by an alligator on Lake Kissimmee, which is connected to Lake Okeechobee.
The alligators in Lake Okeechobee are dangerous, but so is the algae. The lake frequently experiences harmful algal blooms, particularly those dominated by blue-green cyanobacteria. The algae can produce microcystin, which is a toxin that can cause hives, nausea, vomiting, diarrhoea and fever. So, if the ‘gators don’t get you, the algae just might.
Kawah Ijen
By night, blue flames dance across the surface of this Indonesian volcanic crater lake, but don’t get too close. This is the largest and most acidic crater lake in the world.
Gases released from the magma chamber of the volcano below, travel up through its vents and belch into the water, where they react to form sulphuric acid and hydrochloric acid. With a pH of 0.3, this makes Kawah Ijen more acidic than battery acid.
Some of the gases bubble to the surface, where they pose a danger to the local wildlife. Birds have been known to die and fall into the lake after breathing its fumes. Meanwhile, human visitors who trek to the crater, are given gas masks to protect them.
When the escaping hot gases hit the oxygen-rich air, they ignite and burn with a neon flame. This creates the blue blames that are visible at night. Some of the gas also condenses into liquid sulphur, which continues to burn blue as its flows down the mountainside. A spectacular if dangerous sight!
Gaet’ale Pond
The Dead Sea may be famous for its salinity, but the crescent-shaped Gaet’ale Pond, in Ethiopia, takes saltiness to new levels.
The Dead Sea, itself a landlocked lake, has a salinity of 34.2% and a depth of 304 metres. This makes it the deepest hypersaline lake in the world. Gaet’ale Pond, however, has a salinity of 43%. This makes it the saltiest body of water on the planet, and more than 12 times saltier than the sea.
The salts in Gaet’ale Pond are mainly calcium chloride and magnesium chloride, but it also contains small amounts of iron which react with the chloride ions to give the water its yellowtinge. The only species that can survive in the lake are single-celled microorganisms, whilst life on its banks is also precarious. The lake emits bubbles of toxic gases, which can suffocate insects and small animals on its shores.
Lake Lugano
Humans have a terrible history of polluting the environment, creating danger for both ecosystems and the living things they contain. This legacy can be seen in the waters of Lake Lugano, a glacial lake on the Swiss-Italian border, which contains the highest microplastic concentration of any known lake.
Microplastics are tiny pieces of plastic debris. Levels in Lake Lugano are twice as high as other Swiss lakes, and six times the worldwide average. Various factors contribute, including littering, stormwater runoff and the tainted wastewater released from treatment plants.
When aquatic creatures ingest these microplastics, it can reduce their fertility, slow their growth and cause damage to their internal organs. When people eat these animals, the microplastics can enter the body, where they have the potential to cause health problems. Now some experts believe we are in the middle of a plastic health crisis.
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Main image: Aerial view of Misty Volcano of Kawah Ijen crater in East Java
