8 Lakes Where a Dive Could Be Deadly

A smoldering lake on a cloudy day

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Lakes can be special places that make you reminisce about family vacations or memorable summer camp stays. But not all lakes have the allure of those with tree-lined shores. Some lakes get rough when bad weather approaches, and those fed by glacial springs can be dangerously cold (albeit beautifully clear).

And then there are lakes that are downright deadly. Some lakes are so lethal that merely standing on the shore could mean death. Acidic water or volcanic fumes bring serious dangers, and there are examples of lakes with high concentrations of gases literally exploding.

Here are several lakes you certainly wouldn't want to swim in, and where it might be lethal to even stand on the shore or breathe the air.

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Kawah Ijen crater, Indonesia

Photo: R. M. Nunes./Shutterstock

Kawah Ijen is an Indonesian volcano that has the world’s largest acidic lake. The crater lake’s water is a bright — dare we say inviting — turquoise color. A swim would not be wise, however. Not only does the acidity in this lake eclipse lemon juice, the water is more dangerous than battery acid. The lake affects local life in the region. Even far downstream, farmers have to deal with abnormal pH levels in their irrigation water. Closer to the volcano, miners work to collect hardened sulfur. The presence of toxic gases makes this a very dangerous job, especially since most workers do not wear masks, but only cover their faces with cloth.

The sulfur inside Ijen catches fire when it comes into contact with the air. This creates a unique phenomenon: The gases burn with an intensely blue flame. The dangerous but beautiful light show is visible at night.

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Laguna Caliente, Costa Rica

Photo: wiredtourist.com/flickr

The Poas Volcano, in central Costa Rica, has two crater lakes. Botos Lake is in an inactive crater that has not erupted in thousands of years. This is a pleasant place with clear water surrounded by a lush cloud forest. The other crater lake, Laguna Caliente, is very different. This is one of the world’s most acidic lakes, with an acid content higher than a car battery. Obviously, you would not want to swim in the water, but the lake can create acid rain and acid fog that can affect people even if they are not near the shoreline.

It is often impossible to get close to Laguna Caliente. Poas is still one of Costa Rica’s most active volcanoes. Eruptions and activity inside the volcano can cause dangerous gas and ash emissions. For safety reasons, authorities in the national park surrounding the volcano often set up a two-mile perimeter around the crater.

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Lake Nyos, Cameroon

Photo: Bill Evans, USGS/Wikimedia

One of the deadliest lake disasters in recent history occurred in northern Cameroon in 1986. The disaster was caused by a rare phenomenon known as a “limnic eruption.” This phenomenon happens when dissolved CO2 in deep lakes suddenly erupts from the water because of a change in pressure. This eruption, also known as “lake overturn,” creates a large cloud of carbon dioxide, which can suffocate animals and people because the carbon displaces all the oxygen. The 1986 eruption in Lake Nyos killed more than 1,700 people. The gas cloud reportedly spread at more than 60 mph and reached 15 miles from the lakeshore.

Another Cameroonian lake, Lake Monoun, suffered a similar, but less deadly, limnic eruption in 1984. Thirty-seven people were killed. Both these lakes are now the site of gas pumping operations that are meant to prevent future problems. Lake Monoun is reportedly safe now because all the gas has been removed, but pumping operations are ongoing in the larger Lake Nyos. Eruptions will still be possible until all the gas has been removed, but people have resettled the area because they want to farm in its rich soil.

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Boiling Lake, Dominica

Photo: Emily Eriksson/Shuterstock

Boiling Lake is a bubbling body of water on the Caribbean island of Dominica. The lake is a fumarole, a hole in the earth’s crust, that has been flooded by rainfall and fed by two small streams. Underwater lava and gases from the nearby volcano heat the water. Around the shorelines, scientists have measured temperatures of 180 to 197 degrees F (82–92 degrees C). They were unable to obtain readings from the middle of the lake, where the water is actively boiling.

The lake is a popular destination for hikers, who must walk for several hours to reach the site. At 200 feet across, this is the second largest boiling lake on Earth. (The largest is Frying Pan Lake in New Zealand.) A cloud of vapors usually hovers over the lake, and the depths, which are thought to exceed 200 feet, can fluctuate depending on rainfall levels.

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Lake Kivu, Congo and Rwanda

Photo: Gavin Morrison/Shutterstock

Lake Kivu is on the border of the Democratic Republic of Congo and Rwanda. Its area is estimated at more than 1,000 square miles and its maximum depth exceeds 1,500 feet. Like Cameroon’s Monoun and Nyos, Kivu has undergone limnic eruptions, though none has happened recently. Scientists have found evidence that suggests the eruptions have happened about once per millennium. Because of the amount of CO2 and methane in the lake, and a waterside population of more than two million people, a limnic eruption here would be devastating. The loss of life would be much worse than the two 1980s disasters in Cameroon.

Energy companies have been extracting the methane from the lake to use as fuel. This has helped to meet rapidly developing Rwanda’s power needs, and it may also lower the risk of a future eruption. However, there are questions as to whether the extraction will upset the current balance of pressure that keeps the deadly gases deep underwater. In the Congo, the need for energy to spur economic growth makes Lake Kivu’s gases an attractive power source, despite the risks.

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Quilotoa, Ecuador

Photo: Annom/Wikimedia

The Quilotoa crater lake was formed in the 13th century by a massive volcanic eruption. This body of water is known for its picturesque turquoise color. It is difficult to reach because it sits in a rugged area about 12,500 feet above sea level. Most people visit the lake as part of a multi-day trek through the surrounding mountain farmlands.

The biggest danger for visitors is usually altitude sickness. Some of the trails around the lake suffer from erosion, so falling is also a problem. Because of the high acidity, no aquatic life can be found inside the lake. The water is not potable, but advice about entering the lake is contradictory. Some claim swimming is dangerous because of the acidity, while others say the colder temperatures at this altitude will harm swimmers before the water causes any damage. Tourists can take a motor boat cruise on the lake or rent a canoe or kayak and take off on their own.

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Mount Rainier crater, Washington, USA

Photo: National Park Service/Wikimedia

The crater lake near the summit of Mount Rainier is always covered with snow and ice. The lake can only be reached by traveling through a series of caverns. These ice caves can prove deadly because they house pockets of hazardous gases such as carbon dioxide, sulfur dioxide and hydrogen sulfide. Scientists who explore and attempt to map the cave system have to carry gas monitoring equipment so that they can avoid potentially deadly situations while underground.

The sulfuric acid created in the crater lake itself literally eats at the mountain’s volcanic rock. Why would anyone come to such an inhospitable place? Mountain Rainier is popular with alpine-style climbers, who often take shelter in the caves when the notoriously unpredictable weather at the summit turns bad. In addition to volcanologists and explorers, the caves also attract scientists who want to see what microbial life lives in this harsh environment. One of the theories is that the life forms here would be similar to life on other planets.

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Lake Karachay, Russia

Photo: NASA/Wikimedia

Lake Karachay, in the Ural Mountains in Russia, is the most polluted place on earth according to Washington D.C.-based Worldwatch Institute. Waste from a nearby nuclear facility was disposed of in the lake during the Cold War. The radiation levels were so bad that in the early 1990s, anyone who stood on the shore of the lake would be able to live only for about 60 minutes.

In an attempt to control radioactive sediment, authorities started filling the lake with cement. This project was started in the 1970s and seems to have been somewhat successful. Nearby population centers have seen a decrease in radiation-related illnesses and birth defects, and the water in downstream rivers is clean. However, a project to test local groundwater is still in its earliest stages and parts of the lake, though largely sealed off with concrete, remain extremely polluted.