The Dangers and Risks of Deep Sea Diving

dangers and risks of deep sea diving

Nowadays, scuba diving is a popular leisure activity that adults and even teenagers can enjoy. With the proper scuba gear and training, nearly anyone can breathe underwater and explore the beautiful coral reefs, historical wrecks, and view the amazing marine life that you won’t find anywhere else.

Thanks to the numerous innovations of modern scuba equipment, recreational scuba diving can be considered to be a “low-risk” activity. However, it is still not without its dangers and risks, particularly deep sea and technical dives. By knowing about the possible dangers that await you, you can be well-prepared to handle it or avoid it altogether.

Don’t let the worst-case scenarios deter you from diving. As long as you follow safe diving practices, are physically fit, and are confident in your scuba diving ability, you will be able to enjoy all of the wonders that scuba diving has to offer with minimal downsides. Let’s get into the possible dangers and risks you may come across while scuba diving.

Is Scuba Diving Safe?

Once again, modern scuba diving is very safe, so long as you stay within the guidelines.

Few things in life are without risk. Granted, scuba diving is considered to be an “extreme” sport, meaning it is riskier than most, yet hundreds of thousands of certified divers enjoy this activity yearly, with more getting certified each year. Despite so many people participating in this so-called extreme sport, the death rates of scuba divers each year is quite low.

According to the Divers Alert Network’s (DAN) 2017 report, the total amount of reported scuba diving fatalities in the entire world over the previous 10 years is 1,067. That averages out to a little over 100 deaths a year. The United States specifically averages about 70 deaths a year, contributing to 70% of the total number of scuba deaths. While that is statistically alarming if you’re an American, when you consider how many people scuba dive each year, the absolute number is on the low-end.

However, just because you are not statistically likely to die while scuba diving does not mean it is risk-free. On the contrary, there are myriad ways you can expose yourself to danger, and in the next section, we will discuss the most prominent ones and how to avoid them.

Top Scuba Diving Dangers and Risks

Decompression Sickness (‘The Bends’)

Decompression sickness (DCS), often referred to as ‘the bends’ in dive culture, is what you experience when you go from a high-pressure environment to a low-pressure one without decompressing properly. In other words, the bends are what happens when you ascend too quickly. It is a common phenomenon that affects scuba divers and deep-sea divers. It can also affect people at high altitudes. if left untreated, the bends can be fatal.

What’s actually happening inside your body is that when you dive with compressed air for long periods of time, some of that oxygen and nitrogen will get absorbed into your body. While your body eventually uses up all of the oxygen, the nitrogen will get dissolved into your tissues and blood and remain there as long as you remain in the high pressure environment..

When you start your ascent to a lower pressure depth, the excess nitrogen that was absorbed into your blood and tissues from prolonged exposure to high pressures starts to get released. This process should be done slowly, but on a rapid ascent, the lingering nitrogen forms into bubbles which can accumulate in your joints, heart, lungs, spine, and even brain. This can cause blockages which can be potentially fatal.

Common symptoms of the bends are muscle and joint pain, nausea, headaches, memory loss, shaking, loss of hearing, and many more. It also commonly causes your joints to be immobilized in a bent appearance, which is what the term ‘the bends’ is referring to. Sometimes symptoms can occur 48 hours after a dive session. Some cases are serious, perhaps even life-threatening.

If you or someone you know starts to experience these symptoms, provide them with an oxygen mask if one is available, and call emergency medical services immediately.

In order to avoid the bends, you should ascend slowly and adhere to your No-Decompression Limits (NDL), and perform decompression stops when necessary. If you are wearing a dive computer, the computer can calculate this information for you and warn you when you are ascending too quickly and when you should do a deco stop. You should also be well-hydrated, reasonably fit, well-rested, and avoid consuming any drugs or alcohol prior to a dive.

Performing the steps above will drastically reduce your chances of getting the bends, though it may still happen randomly. There are also some individuals who are at higher-risk of experiencing DCS. For instance, those with a history of heart or lung conditions, a history of alcohol or tobacco use, poor cardiovascular fitness, a high body-fat percentage, existing injuries, over the age of 30, and are female, are more likely to experience DCS.

Read this article for more tips on how to avoid the bends.

Lung Over-Expansion

As you dive deeper and the water pressure increases, both your lungs and the air you breath becomes highly compressed. Lung over-expansion is what occurs when you hold your breath as you ascend. Your lungs and the air inside should both expand as the pressure decreases. However, when you hold your breath, you are forcing your lungs to stay contracted while the air inside keeps expanding. Once the air expands too much, it can rupture your lungs which can be fatal.

To avoid this, make sure you are always continually breathing. As a general rule of thumb, do not hold your breath. If for some reason you need to hold your breath while ascending, only do so after you have exhaled. This way, there will only be a limited amount of air remaining that expands, and it should not be able to damage your lungs. With that said, holding your breath and depriving yourself of fresh oxygen comes with its own share of risks, so the easiest solution is to always be breathing.

Be very careful about ascending if you have asthma. When you are experiencing an asthma attack, your airways will be constricted and airflow may be partially or completely stopped, which is essentially the same as if you were holding your breath. Divers who panic and try to surface quickly put themselves at risk of a lung over-expansion injury as well as decompression sickness.


Barotrauma of the middle ear is a common health risk of scuba diving caused by underwater pressure. One can experience multiple types of barotrauma other than the ear, such as sinus, teeth and lung barotrauma. Basically, anywhere in your body that holds pockets of air can experience this risk.

When you dive, the air in your body gets compressed from the pressure. This sensation, if not equalized, can lead to extreme pain, bleeding, fluid buildup, and even hearing loss. As you descend, you must remember to equalize your ears by pinching your nose and blowing from it (a.k.a. the Valsalva maneuver). There are also various equalizing maneuvers you can attempt which you can read about here.

If for some reason you cannot equalize your ear using any of the equalization methods, stop your descent immediately. If you still can’t figure it out, then it’s best to end the dive.

Nitrogen Narcosis

Nitrogen narcosis is known by many names. Some call it the Martini effect, others call it the rapture of the deep, basically names which reference some kind of drunkenness or state of euphoria. To be honest, it almost sounds very pleasant. Don’t be fooled, it can possibly lead to your death.

As the slang names imply, nitrogen narcosis is a temporary condition similar to being drunk that affects divers at depths of approximately 25m (82ft) and beyond. This occurs when one inhales gases at a higher partial pressure. The symptoms include euphoria, poor judgment, disorientation, difficulty focusing, hallucinations, and many more out of body experiences. None of these symptoms directly harm you. Instead, it is the poor decisions that result from your impaired state that can be deadly.

Experienced divers require special training in order to resist these symptoms or to function in spite of them. Deep sea divers will use a heliox gas mix (a mixture of helium and oxygen) because helium has been found not to cause inert gas narcosis. Unfortunately, helium is incredibly expensive, so it’s not something you want to regularly use. Furthermore, this condition typically resolves itself on the ascent. Keep in mind, ascending too quickly puts one at risk of decompression sickness.

Sometimes nitrogen narcosis and decompression sickness get mixed up since they are both caused by excess nitrogen gas in the body.

Gas or Air Embolism

When one ascends too quickly, nitrogen will get released as bubbles and these bubbles can block your arteries, cutting off blood supply. As we mentioned above, this is one of the lethal side effects of decompression sickness. Also, if you hold your breath and the air in your lungs continue to expand, rupturing your lungs, some of the air bubbles can then enter your bloodstream and cause a blockage from there.

When you experience a gas embolism, some of the symptoms are an irregular heartbeat, blurred vision, anxiety, and chest pain, among others. Treatment involves being put into a 100% oxygen, hyperbaric pressure chamber.

Air or gas embolism can be easily avoided by staying within your depth limits, ascending slowly, breathing normally, and not diving with a pre-existing heart or lung condition. Basically, as long as you are trying to prevent DCS, you should also be safe from gas or air embolisms.

Oxygen Toxicity

If you are a recreational diver, you will most likely never encounter this, however deep and technical divers are susceptible to this. Oxygen toxicity is a medical condition that can occur with divers who perform open-circuit, rebreather, and Enriched Air Nitrox (EAN) dives using mixed gases with a high concentration of oxygen. Too much oxygen can be toxic and negatively impact the body.

There are two types of oxygen toxicity to worry about: Pulmonary Oxygen Toxicity (POT) and Central Nervous System Oxygen Toxicity (CNS), the latter being the more common condition. When diving at extreme depths where vision and communication is limited, it’s important to be able to recognize the signs of oxygen toxicity. Symptoms include nausea, twitching, visual disturbances, irritability, and dizziness.

Even with preventative measures, there’s no guarantee that divers can remain unaffected by oxygen toxicity. However, you can minimize the risk by staying within your depth limit, using a dive computer to track your metrics, monitoring your gas consumption, conserving your energy, and breathing properly.

Running Out of Breathing Gas

Divers who lack experience or don’t dive with a submersible pressure gauge (SPG) can sometimes find themselves out of breathing gas. There is a reason why SPGs are a mandatory piece of scuba equipment. You will notice that all SPGs have a red marker spanning the 500 psi (50 bar) remaining mark, which is when the air supply is running dangerously low. At this point, you should begin your ascent because you don’t know what issues may arise on the way up.

The most common cause of running out of breathing gas is simply poor gas management. Divers who rely on a dive watch which only tracks the time, not the actual remaining gas supply as SPGs do, can find themselves unexpectedly out of air. You must regulate your breathing and try not to exert yourself if you don’t need to. Staying calm is a must to keep your base heart rate low. For peace of mind, you may want to dive with a reserve air tank in case of equipment malfunction or poor gas management.

Recreational divers commonly dive with just air. Commercial, tech, and wreck divers will typically dive with various gas mixes to help them stay underwater longer. Whatever the case, it is a good idea to surface before you need to because waiting until the last moment is too risky.


If you are diving in cold waters, you can potentially develop hypothermia. What many don’t realize is that “cold” water doesn’t even have to be that cold. Water is colder than your body’s core temperature, and it is incredibly effective at decreasing it (about 20x faster than air). Thus, even if you were to dive in tropical waters, if you stay in it for too long then you may find yourself shivering and with symptoms of mild hypothermia. You should be aware of hypothermia symptoms so that you can ascend before it sets in.

To prevent hypothermia, divers should be prepared for the environment they will be diving in. Too many underestimate how cold even tropical waters can be. To be safe, divers should wear a full wetsuit to conserve their body heat. If necessary, you can also wear a dive hood and dive gloves to cover up the portions of your body where a majority of heat loss occurs.

Entanglement and Entrapment

With all of the scuba equipment divers need to carry around, it’s very easy for them to get entangled in nets, kelp, or anything stringy. That’s why it’s important to carry a dive knife and to be able to easily access it. Using the dive knife, you can sever the object that’s tangling you up and avoid a fatal outcome.

Similarly, when you are diving in an environment where there is little to no visibility, and vertical access to the surface is unavailable, there is an inherently high risk of entrapment. Divers who want to dive in caves, caverns, wrecks, or swim under ice must be hypervigilant about their surroundings so that they don’t get stuck. Proper training is required, as is specialized gear. Divers must also thoroughly plan their dive and dive with a team.

According to the Divers Alert Network, entanglement and entrapment account for approximately 20 percent of scuba diver deaths. Once a diver is trapped, they run out of air and die from asphyxia or drowning.

Getting Lost/Diving Alone

It’s scary enough to get lost in a foreign environment on dry land. When it happens to you underwater, it may be fatal. No matter what, you must remain calm and try to relocate your dive buddy or group. If you are alone, and any of the dangers and risks outlined in this article happens to you, then there would be no one around to save you and your chances of survival drop to nil.

Despite knowing to stay together, sometimes divers can separate from a group because they were too busy exploring and wandered off too far. In very rare circumstances, the dive boat may not realize a crew member is missing and leave. In even rarer circumstances, a boat may have to abandon some divers and return for them later.

As part of the dive planning, the group should agree on the procedure to follow if someone gets left behind. What happens if you surface and find the boat missing, or if you find yourself separate from the group? These things can sometimes happen, and having a plan can help you stay calm and eventually regroup. Discuss what signals to use so that some communication is possible underwater.

If you are thinking about diving alone, or feel like straying from the group, as a beginner you should never even consider it. When diving with a group, always keep an eye out for your fellow divers, not just for your own safety, but theirs. When diving with less experienced members, go over with them the various scenarios that may occur and how to respond to it. Getting lost or separated from the group is scary but, with proper training and coordination, it should be an easy one to recover from.

Malfunctioning Equipment

Before heading into the water, you must do a pre-dive check. This is something you must take seriously. It is better to find any defective equipment while you’re safe at the surface, rather than finding out something isn’t working 100 feet underwater. The most common equipment failures are: ruptured regulator hose, broken O-ring, as well as jamming and closing of the cylinder valve.

Some particular pieces of equipment to focus on are your dive computer, BCD, SPG, scuba tank and regulator. You want to make sure your dive computer is providing you the correct information. If it is calculating inaccurate no-decompression limits, it puts you at increased risk of DCS. If your pressure gauge is malfunctioning, you may suddenly find yourself out of air underwater.

Even if a piece of equipment appears to be working fine, examine it thoroughly for any cracks, tears, discolorations, and any imperfections that you suspect may worsen during a dive. If you’re renting equipment, ask for a new one.

When it’s your own equipment, you should be taking proper care of it so that it doesn’t reach this point. You should also have your gear serviced by a certified technician from time to time. For instance, scuba tanks need to be visually inspected once a year and hydro tested every five years to be considered safe. Similarly, your dive computer may need to be calibrated once a year to ensure it is still displaying accurate data.

Lastly, sometimes even if you do your due diligence, equipment failure can still happen. Perhaps it gets damaged when it comes into contact with something or an unexpected leak happens. For the most crucial pieces of equipment, it’s not a bad idea to have a backup. For instance, you can bring along a pony bottle and a spare dive computer in case the main one fails.

Strong Currents

If you find yourself caught in a current, it can be one of the most physically demanding, unpredictable, and terrifying encounters you can have as a diver. Fighting against a current will rapidly drain your energy, causing accelerated gas loading, exhausting, and separation from your group. It may even sweep you so far away that you can’t return to your boat.

Those diving in currents, particularly drift divers, must have at least a general understanding of how to dive in a current. Bottom currents and surface currents do not necessarily travel in the same direction, for example. Some may also reverse directions during a dive.

When caught up in a current, you must do everything in your power to get out of it. Try to grab onto to slow your pace. If possible, try to hide behind an object such as a large rock or a wreck. Taking shelter can almost completely remove the current. However, if this isn’t possible, then at least swim to the bottom where it isn’t as strong.

It is possible to go along with the current, turning your dive into a drift dive. However, you should only do this if you know it is possible to safely exit the current. If you need to fight against the current to escape it, then it is extremely dangerous. If there are too many currents where you’re diving, you should consider ending the dive.

Dangerous Marine Life Encounters

You’re literally out of your element in the water. Every time you submerge, you enter a world that isn’t yours; an untamed wilderness that you know little of and is home to many creatures that can react in unpredictable ways. Most creatures are quite shy and timid. If you leave them alone, they will leave you alone. If you try to interact with them, however, they may feel threatened and react defensively.

Furthermore, some marine life might be territorial. Imagine how you would react if a strange creature suddenly entered your home. You may feel a sense of curiosity and wonder, or the encounter can go in a different direction; fear, anger, anxiety. Again, it’s impossible to predict how the fauna will react to you.

The best thing to do is to keep a safe distance from both the fauna and flora. You don’t know how they will react to you, but it’s possible your presence can be harming them as well. Some animals will bite or inject you with poison. Even corals can cause lacerations and stings. Be vigilant of the marine life nearby and treat them with respect as well as a healthy dose of fear. It’s best to follow the old adage, “Look, but don’t touch.”


Unsurprisingly, the most common cause of scuba diving deaths is drowning. Drowning can easily occur if a diver encounters any of the risks and dangers outlined in this article. However, what precedes drowning is an unexpected medical condition. Many victims of drowning were found to have suffered a heart attack which incapacitated them, leading to their deaths in the water. If you have pre-existing medical conditions, consult with your doctor and let them clear you for diving.

Other common causes of drowning are equipment malfunction, rough waters, loss of consciousness, gas-supply problems, and so on. Diving with a buddy can go a long way to prevent drowning incidences. Keep an eye out for each other and be aware of when someone is in distress. Furthermore, regular doctor checkups can help you manage your health conditions that can result in incapacitation.

Displacing the Second Stage

Sometimes the second stage can get displaced from your mouth. This can occur by accident by impact with another diver or through your own arm movements. It may also get entangled in kelp or blown away by a sudden current. Very rarely, you may simply lose consciousness from a medication condition and release your grip on the regulator.

When you lose your second stage regulator, you must remain calm and perform the regulator recovery skill you were taught in diving school. In most cases, you should be able to quickly recover your second stage. If you require assistance, quickly signal to your diving buddy that you are in distress. In the meantime, do not hold your breath and continue exhaling slowly.

Saltwater Aspiration

A rare but dangerous disorder that few divers will experience is saltwater aspiration. This occurs sometimes when divers inhale a mist of saltwater. The most common cause of saltwater aspiration is due to poor diving technique, faulty equipment, and near-drownings. This disorder has damaging effects on the diver’s lungs. Symptoms of seawater aspiration are similar to decompression sickness which can make it hard to diagnose.

When inhaling saltwater, bodily fluids can potentially move from your lungs to your breathing spaces, impeding your ability to breathe. Most people only have mild reactions to inhaling saltwater, and the symptoms resolve themselves shortly. On the other hand, some divers have more severe reactions and need to seek medical attention.

Dysbaric Osteonecrosis

Dysbaric osteonecrosis (DON) is a disease which causes bone necrosis, and those who have been exposed to changes in pressure over many years can sometimes suffer from it. This disease is more likely to affect professional divers than casual, recreational ones. Workers who have to work with compressed air are most susceptible. In the case of divers, divemasters are the ones more likely to develop it.

It is currently theorized that this disease is linked with decompression sickness, however no conclusive evidence has been observed. The general assumption is that the development of DON has to do with being exposed to high pressure for prolonged periods of time.

As such, tech and deep divers who regularly dive to depths of 100ft (33m) or more should consider getting their bones checked every few years. Those who find themselves regularly experiencing the effects of mild decompression sickness should also consider doing this.

Caustic Cocktail

Divers who dive with a rebreather may find themselves exposed to a caustic cocktail. This is what happens when the absorbent material that filters the carbon dioxide from breathing gas gets flooded with water. The contaminated water makes its way through the hose into the diver’s mouth. The short term effect is simply choking, however the caustic cocktail may also damage the lungs.

To prevent this, regularly check the rebreather for leaks and close the surface valve when it’s not in use. If the caustic cocktail enters your mouth, rinse your mouth and switch to a backup tank if you have one so as not to breathe contaminated air anymore.

Boat Collisions

Lastly, divers can sometimes fall victim to boat collisions and boat propeller strikes. In the U.S. alone, dozens of deaths occur each year from this. The risk of a boat collision is higher in areas where multiple boatloads of divers congregate to share the same dive site. Even coming into contact with a small boat can be fatal.

To prevent accidents in areas with high boat traffic, both the divers and boaters need to be cognizant of their surroundings. Divers must look around before surfacing. Boaters must look out for any dive flags marking areas where divers will surface. Accidents can be prevented as long as all parties involved are following safe diving and boating practices as well as being aware of their surroundings.