Almost three-quarters of our blue planet is covered in water, and—for an equally accurate and verifiable statistic—absolutely every inch of it is terrifying and evil. Much of Earth’s water is unexplored, deep, dark, frigid, and home to nightmare-inducing creatures that float through the seas like slimy ghosts. Even the shallows we’re familiar with can come with treacherous rapids, hidden caves, boiling vents, noxious gas plumes, and more. Despite all this, diving is still a very popular pastime.
Millions of divers take to the water every year to get into any body of water they can. Many return with a lifetime of memories and beautiful photographs. However, many also die. Each year, they average between 100-200.
This list includes spots that have been taken by divers as well as those with untapped potential for lethal diving, but they all make up some of the most dangerous places you can scuba dive.
10 Chuuk Lagoon
Chuuk Lagoon—formerly Truk Atoll—is a set of islands and coral reefs within the Federated States of Micronesia. It is actually an ideal place to scuba dive in so many ways—it boasts clear blue water, an impressive assortment of marine life, and an entire fleet of sunken ships at which to marvel. However, if there’s one small, itty-bitty catch to the lagoon, it would have to be thousands of bombs, grenades, mines, depth charges, torpedos, and other explosives scattered throughout its area.
During World War II, Chuuk Lagoon played host to the Empire of Japan’s main naval base. The U.S. Navy destroyed the base in 1944 and made it inoperable. The New York Times’s words, “the biggest graveyard of ships in the world.” Perhaps the most dangerous aspect of the Chuuk graveyard is just how much of its contents are still a mystery; several major ships, alongside their explosive cargo, are still missing. The same applies to aircraft and tanks.
9 Citarum River
The Citarum River, one of the largest in Indonesia, is one of the entries on this list that probably doesn’t get many scuba divers as is. However, anyone who dares to attempt it would quickly discover why the Citarum is the most polluted river on the planet.
There are more than 2,000 factories that dump waste into the river every day, an estimated 20,000 tonnes. Many stretches of river are now unrecognizable as water. Instead, they’re covered in plastics, styrofoam, and other non-biodegradable garbage. Even clearer waters can still be deadly. Nearly every gallon of the tragic Citarum River contains mercury, PCBs or lead.
8 Bolton Strid
The River Wharfe flows over 60 miles through England’s Yorkshire area. It is picturesque, idyllic, tranquil, and serene for most of its length. This is true only on its banks and surface, as the river’s deeper parts can prove deadly. So deadly that the river has earned two dubious distinctions: “one of the deadliest bodies of water in the world” and, for those who fall in, a “100 percent mortality rate.”
The Strid’s lethality comes from the fact that, in some areas, an otherwise 30-foot-wide river is condensed into a mere six-foot width, leading to an instant and exponential increase in current, pressure, and number of whirlpools. To top it off, several stretches in the faster parts of the Strid—though still only around six feet wide—reach tens of meters in depth. The waters at the bottom can be fast, cold, fast, chaotic, and can lead to many deaths.
7 Lake Karachay
It may surprise you to learn that the #7 entry was recently filled with concrete, depending on your reasons. It is no longer safe to dive. But for about 65 years, Russia’s Lake Karachay may very well have been the single most dangerous body of water in the world. It was so hazardous that even filling it in completely didn’t remove its lethality.
From 1951 to 1957, Lake Karachay was used by the Soviet Union as a dump site for nuclear waste. The Kyshtym catastrophe further contaminated the area, bringing its baseline radiation levels up to near-Chernobyl. The radiation from Lake Karachay could kill an individual in less than an hour at its peak in the 1990s. The entire area is now radioactive and off limits.
6 The Eagle’s Nest
The Eagle’s Nest in remote Florida is a system of underwater caves that makes many “deadliest” lists, and with good reason: its deceptively simple surface level quickly descends into one of the deepest, darkest, deadliest scuba locations in the world.
The sinkhole appears from its banks to be a typical small pond. But anyone who dives into this pond quickly discovers the truth: the water falls straight down, more 300 feet into blackness. Even without considering the narrow passageways and twisting that divers must follow, there is a high chance of death from depth intoxication at that level. At least ten professional divers have died exploring The Eagle’s Nest.
5 Battery Acid Bath
Technically, this entry contains more than one, but all of them share one deadly property: acidic water. Their water is more acidic or more concentrated than battery acid for some of these caustic organisms.
Water can become excessively acidic in many ways. However, one method is to drain the water from a nearby mine. The worst culprits are coal mines, which inadvertently (and often purposefully) dump acidic metals or sulfides into lakes and rivers. The result can sometimes be beautiful, turning rivers deep reddish, orange, yellow or green. These waters are dangerous and can lead to death. One mine in Iron Mountain, California, was found to have the most acidic water ever discovered. Its pH is -0.7
It’s likely you just learned that the pH scale can go below zero, and that should tell you how dangerous these waters can be.
4 Lake Nyos
If a body of water causes such widespread water loss that it is named after a famous disaster, then you can be sure that staying away from its water is a wise decision. In 1986, Lake Nyos in northwestern Cameroon did just that when the “Lake Nyos Disaster” killed more than 1,700 people.
Essentially, Nyos’s waters have the misfortune of resting above pockets of underground magma, which constantly leak CO2 upwards. The lake is susceptible to a rare phenomenon called a limnic explosion, which causes large amounts of CO2 to be absorbed into the water and then suddenly erupt from it as a cloud. This cloud, some 100,000-300,000 tons of CO2, shot out of the Lake’s waters, spread throughout the immediate area, including several local villages and 1,746 people.
Take care when you dive in.
3 The Boiling Lake
The lake’s name says it all on this one. Boiling Lake is hidden in the lush, tropical mountains on the Dominica island. This title is not metaphorical. Essentially, it’s a flooded fumarole.
Though it’s hard to find any recent records of the water’s temperatures, as presumably, scientists are more rational these days, a record from two scientists in 1875 put the temperature at the water’s edge at 180 to 197 degrees Fahrenheit. They were unable to record temperatures further in the lake because the water was boiling. This caused damage to their instruments and their bravery.
2 Iceberg B-15
Iceberg B-15 is a transitional iceberg that moves from one extreme to the next. It covered more than 3,200 miles and was the largest iceberg ever measured. Eventually, enough pieces broke off to give another crown. B-15 had caves and water. People caved in it.
Three filmmakers National Geographic decided to dive into the icy, black waters inside the iceberg’s caves, and their account of the trip is harrowing. Some tidbits, as terrifying as they are tantalizing, from diver Jill Heinerth are as follows: “One minute is dangerous. I mean you very, very quickly lose the ability to manipulate your hands or operate or even think straight,” “There were also strange cracks and pops and groans from the ice. It was moving, it was shifting, it was changing,” and “The cave tried to keep us today.”
1 The Blue Hole
If you’re familiar with scuba diving, or even just the bevy of “Most Extreme” specials that Nat Geo airs on a loop, then you’re likely not surprised that the Red Sea’s blue hole makes the top spot on this list. If you are surprised, it’s likely that you don’t know the site by either of its nicknames: “World’s Most Dangerous Dive Site” and “Divers’ Cemetery.”
Blue holes are large marine sinkholes that cause water to quickly drop into darkness and crushing depths. They can be found all over the globe. Many blue holes have earned a reputation for divers, but none more than the one off the coast of Dahab in Egypt. Its exact body count is unknown, but it is estimated to number around 200.
Although the challenges are simple, they can be deadly. According to diving instructor Alex Heyes, divers attempting to swim under the hole’s rocky arches are often unaware that “this challenge is to scuba divers what Kilimanjaro is to hikers.” And as such, the fatalities continue.