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Let's take a closer look at how long the human body can withstand underwater pressure
Most people have likely watched a "deep-sea" movie at some point, such as Secret of the Deep, Sanctum, or similar games.
But the question always arises: Can humans survive at great depths for extended periods? Let’s examine this issue in detail and refer to scientific sources. The key concern here is: How deep can the human body withstand pressure?
Clearly, the main issue is mechanical pressure. Water can exert extreme force on a person, potentially leading to fatal consequences. However, pressure itself isn’t the most dangerous factor for divers.
There are aspects we may not even consider, but surprisingly, they are purely physical phenomena!
Most of the human body can handle pressure well because we are primarily composed of water. Of course, we must balance the air in our sinuses and ears while diving. However, as most divers experience, this is most noticeable near the surface, where the pressure changes significantly per meter.
If we properly equalize the pressure, we can endure high-pressure conditions in most cases. Sudden depth and pressure changes can be painful or dangerous (especially near the surface), but we adapt to pressure changes fairly well given enough time.
At a depth of 30 meters, where the pressure is four times that at sea level, nitrogen intoxication can occur. This happens because we inhale approximately 3.12 times more nitrogen than normal. (Interestingly, we still don’t fully understand the phenomenon of nitrogen narcosis.)
For recreational diving, the safe depth limit is 40 meters due to the risk of nitrogen intoxication. At lower levels (30–50 meters), the effects are similar to nitrous oxide (laughing gas) exposure, but at greater depths (100 meters), it can be lethal. However, most trained divers can survive these conditions.
At a depth of 60 meters, oxygen toxicity becomes an issue. This occurs because, at seven times the surface pressure, a diver breathes 147% oxygen—nearly 1.5 times the amount inhaled when breathing pure oxygen at the surface. (Contrary to popular belief, 100% oxygen is safe for short-term use at normal atmospheric pressure, but at 1.4–1.6 atm, it becomes a completely different gas with toxic effects.)
This is why deep-sea divers use gas mixtures instead of regular air. Interestingly, at extreme depths, divers must inhale gases that could cause dangerous oxygen deprivation at the surface.
Simple diagram for proper diving.
Another significant risk for deep divers is High-Pressure Nervous Syndrome (HPNS). This condition results from the effects of deep diving (from 120–130 meters) with helium-based breathing mixtures on the nervous system. Symptoms include tremors in the limbs and torso, reduced concentration, impaired cognition, drowsiness, and even unconsciousness. At this depth, HPNS can become severely debilitating.
Even if we could overcome HPNS, helium intoxication at extreme depths could be another deadly obstacle. Although helium is considered the least narcotic gas (with a narcotic index of 0.045 compared to nitrogen’s 1.0), estimates suggest it may become dangerous at depths of 2,000 meters. However, these are purely theoretical figures, as no human has ever reached this depth without a submarine or deep-sea suit.
If breathing normal air, the maximum safe depth is approximately 60 meters. With the best available technology and specialized gas mixtures, the deepest simulated dive reached around 500 meters—but even then, safety was a major concern.
If we could somehow solve HPNS, theoretically, humans might be able to dive as deep as 2–4 kilometers (200–400 atmospheres of pressure). However, at such extreme pressures, even helium could become lethal.
Most people have likely watched a "deep-sea" movie at some point, such as Secret of the Deep, Sanctum, or similar games.
But the question always arises: Can humans survive at great depths for extended periods? Let’s examine this issue in detail and refer to scientific sources. The key concern here is: How deep can the human body withstand pressure?
Clearly, the main issue is mechanical pressure. Water can exert extreme force on a person, potentially leading to fatal consequences. However, pressure itself isn’t the most dangerous factor for divers.
There are aspects we may not even consider, but surprisingly, they are purely physical phenomena!
Most of the human body can handle pressure well because we are primarily composed of water. Of course, we must balance the air in our sinuses and ears while diving. However, as most divers experience, this is most noticeable near the surface, where the pressure changes significantly per meter.
If we properly equalize the pressure, we can endure high-pressure conditions in most cases. Sudden depth and pressure changes can be painful or dangerous (especially near the surface), but we adapt to pressure changes fairly well given enough time.
The More Serious Issue: Gas Toxicity
However, there’s a far greater concern. We might not realize it, but with each breath underwater, we inhale much more gas than at the surface.At a depth of 30 meters, where the pressure is four times that at sea level, nitrogen intoxication can occur. This happens because we inhale approximately 3.12 times more nitrogen than normal. (Interestingly, we still don’t fully understand the phenomenon of nitrogen narcosis.)
For recreational diving, the safe depth limit is 40 meters due to the risk of nitrogen intoxication. At lower levels (30–50 meters), the effects are similar to nitrous oxide (laughing gas) exposure, but at greater depths (100 meters), it can be lethal. However, most trained divers can survive these conditions.
At a depth of 60 meters, oxygen toxicity becomes an issue. This occurs because, at seven times the surface pressure, a diver breathes 147% oxygen—nearly 1.5 times the amount inhaled when breathing pure oxygen at the surface. (Contrary to popular belief, 100% oxygen is safe for short-term use at normal atmospheric pressure, but at 1.4–1.6 atm, it becomes a completely different gas with toxic effects.)
This is why deep-sea divers use gas mixtures instead of regular air. Interestingly, at extreme depths, divers must inhale gases that could cause dangerous oxygen deprivation at the surface.
Deeper Dives and Their Hazards
In controlled environments and with deep-sea diving suits, people can reach greater depths. However, this process resembles being in a "submarine" rather than actual deep-sea diving since the suit shields the diver from direct pressure exposure.Simple diagram for proper diving.
Another significant risk for deep divers is High-Pressure Nervous Syndrome (HPNS). This condition results from the effects of deep diving (from 120–130 meters) with helium-based breathing mixtures on the nervous system. Symptoms include tremors in the limbs and torso, reduced concentration, impaired cognition, drowsiness, and even unconsciousness. At this depth, HPNS can become severely debilitating.
Even if we could overcome HPNS, helium intoxication at extreme depths could be another deadly obstacle. Although helium is considered the least narcotic gas (with a narcotic index of 0.045 compared to nitrogen’s 1.0), estimates suggest it may become dangerous at depths of 2,000 meters. However, these are purely theoretical figures, as no human has ever reached this depth without a submarine or deep-sea suit.
What Depth Is Considered Lethal?
This question isn’t easy to answer. Theoretically, water pressure alone wouldn’t automatically crush a human body. However, in practice, many other factors come into play, including the toxic effects of gases and High-Pressure Nervous Syndrome.If breathing normal air, the maximum safe depth is approximately 60 meters. With the best available technology and specialized gas mixtures, the deepest simulated dive reached around 500 meters—but even then, safety was a major concern.
If we could somehow solve HPNS, theoretically, humans might be able to dive as deep as 2–4 kilometers (200–400 atmospheres of pressure). However, at such extreme pressures, even helium could become lethal.
