What Happens When You Scuba Dive in a Tsunami

“Suddenly I was thrown back. It’s difficult to explain the feeling underwater – imagine running at full speed against the wind and still being pushed back, against an enormous, invisible force that is simply impossible to overcome. While being dragged back and up toward the surface, I tried to find [my girlfriend],” wrote Yossi Hasson in Haaretz online magazine, recounting his experience of being underwater at Koh Phi Phi when the 2004 Indian Ocean tsunami hit. “It turned out she didn’t have time to cross the coral walls. Instead, she caught hold of a cable that was tied to a buoy, because she knew what she had to avoid – ascending too quickly, lest she suffer the bends.”

There are myriad wild theories on how to survive a tsunami. These horrific, destructive seismic sea waves that tear through coastal settlements and wipe out buildings, trees and human lives. As we write this, the warning sirens on the northeastern coast of Japan are wailing as a 7.4-magnitude earthquake has triggered a tsunami. As civilians seek higher ground, and leave behind their homes for what could be the last time, once again the world nervously waits to see what impacts an earthquake of this size will bring.

As a diver, chances are you’ll spend many a diving vacation at the coast. To help you identify and understand the effects of a tsunami strike whilst you are diving, we bring you all the information on what to look out for and the risks:

The moment the 2004 Indian Ocean tsunami strikes Ao Nang, Krabi Province, Thailand © David Rydevik/Wikimedia Commons

What is a tsunami?

Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the deep ocean, tsunami waves do not dramatically increase in height. But as they travel inland, the waves quickly increase in height as the water depth decreases, giant walls of water potentially smashing the coast. At the same time, the speed of tsunami waves also depends on depth rather than the distance from the source of the wave. In deep water, tsunami waves can travel as fast as commercial planes; it’s only when they reach shallow water that they slow down.

Warning signs

Tsunamis can strike at any time, but they sometimes come with warnings – when on dry land, check for these scenarios:

  • Severe ground shaking from earthquakes
  • Water receding from the coast and pulling back far enough to expose the ocean floor, reef and fish – experts believe that this could be a “five-minute warning”
  • Abnormal ocean activity: a distant wall of water, a loud roaring sound similar to that of a train or jet aircraft

A village near the coast of Sumatra lies in ruin after the tsunami that struck Southeast Asia in 2004 © Wikimedia Commons

Effects on diving

Tsunamis are much less dangerous when you’re out at sea – it is thought that a diver at a depth of around 20 metres and 200 metres away from land would barely notice what’s going on above. A tsunami can affect the underwater world in a number of ways: If the diver is caught in violently spinning currents, it will feel like they’re in a washing machine turning over and over. If the water is surging in one direction, then the diver will be pushed in that direction. Of course, with this kind of extreme movement underwater, divers can become vulnerable to various dangers.


Those dangers can be fatal, depending on how shallow or deep you are:

  • If you’re deep, a “washing machine” current can pull you up and down – and if you ascend too quickly, you’re at risk of the decompression sickness
  • With the water criss-crossing, it’s easy for your group to be broken apart. Disorientated and pulled by the current, you could end up losing your buddy
  • If you’re too close to powerful tsunami waves, you’re at risk of being dragged inshore onto hard land
  • Just like in drift diving – only much stronger and faster – there is the risk of crashing into underwater structures, being knocked unconscious or sustaining fatal blows

There are stories dotted all over the Internet that tell of divers’ luck in surviving huge tsunamis. Sometimes that is all it really is – luck. But we hope this brief guide will help in your understanding of what is going on, if you are ever unfortunate enough to get trapped within one.

What Happens to Your Body When You Scuba Dive?

Humans have proven to be able to adapt to just about every sort of unique environment the planet earth has to offer. Given that our planet has far more space covered by water than land, it is not surprising that we are able to explore underwater with the use of the right tools. Being able to explore the underwater environment requires specialized gear and training. Scuba gear includes a tank of air for a diver to breathe while underwater.

Physics places restraints on how deep the human body can function underwater. The deeper a diver goes, the more pressure is exerted on the human body and this has implications for the air the diver is breathing from a scuba tank. When the human body is subjected to increased pressure followed by decreased pressure, alarming things can happen to gas molecules trapped in tissues and the bloodstream. This happens due to the physics of increased pressure on the body thereby causing more uptake of gasses into the body fluids and tissues.

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Air is about 20% oxygen and 80% nitrogen. As a diver descends into deeper water, the pressure there increases the amount of gas that enters the tissues of the body. Oxygen is used by cells to generate energy by converting sugar to ATP. So the excess oxygen is partly used up and converted to carbon dioxide which is lost by breathing out. Nitrogen however is inert, it is not metabolized, so the concentrations slowly build up in the fluids of the body as pressure increases.

Biology of the Bends

Problems begin when the diver begins to ascend and the pressure lessens. It takes time for the gasses to leave the body tissues slowly by breathing them out. If the pressure drops suddenly due to a rapid ascent, the dissolved gasses quickly form bubbles which cause all sorts of physiological complications. The effect is not unlike opening a can of soda that has been shaken. Opening the sealed container causes an immediate change in pressure and the bubbles violently form and fizz out all over the place. If a diver comes up from the depths slowly enough, the gasses will have time to make their way to the lungs to be expelled when the diver breathes out. By accidentally skipping this precaution, gas bubbles will form.

The sudden formation of bubbles in blood vessels and body tissues can have significant effects. A person can come down with a set of potentially very serious symptoms collectively referred to as “the bends”. This condition was originally seen in workers constructing underwater foundations for bridges on a riverbed in specially constructed chambers called caissons.

When returned suddenly to the surface the workers would be in intense pain in the legs and knees and would bend over, thus the name. Eventually, this was understood to be caused by gas bubbles in the tissues leading to a condition called decompression sickness.

Decompression Sickness Explained

The broad term for complications due to changes in ambient pressure on the human body is Decompression Illness. There are actually two primary complications involving the formation of gas bubbles inside the fluids of the body. One is Decompression Sickness (DCS), a localized formation of painful gas bubbles. The other is Arterial Gas Embolism (AGE) where gas bubbles enter into pulmonary circulation and are distributed throughout the cardiovascular system by the heart via large, then small, arteries. These gas bubbles can interrupt blood flow to vital organs, much like plaque formation in the vessels of the heart or brain leads to interrupted flow in cases of heart attack and stroke.

Decompression sickness, comes about when gas bubbles form in the tissues and cause localized damage. Gas will collect in joints, distorting them and causing pain. Muscle pain is another symptom as is mottling of the skin as shown here:

These symptoms are commonly called the bends or in diving slang, the person “got bent”. However, DCS can be more severe than just the basic symptoms. Nitrogen gas is readily dissolved in the myelin sheath of nerves and gas bubble formation there can pinch the nerve leading to neurological problems. Some cases have demonstrated dizziness, confusion, even amnesia and unconsciousness. High concentrations of nitrogen can stimulate inflammation responses in tissues. Depending on the concentrations involved, nitrogen narcosis for example, death is a possibility.

As bad as having the bends can be, even worse is an arterial gas embolism (AGE). The leading cause of death in diving accidents, this condition comes from gas bubbles forming in blood vessels which then travel to (or originate in) the lungs. If the gas is not passed on to the alveoli and expelled, the bubbles can make their way to the arterial circulation which interferes with blood delivery to vital organs.

A more dramatic way to introduce bubbles into the arterial circulation is Pulmonary Overpressure Syndrome (basically a burst lung) During an ascent to the surface, external pressure drops and air trapped in the lungs will expand, potentially stretching the tissues to the point of rupture (a pneumothorax). Known as pulmonary barotrauma, it could easily cause a lung to collapse. In this way gas bubbles can make their way into pulmonary capillaries and then to the arterial portion of the circulation to be distributed to arteries leading to the brain and heart.

Just like air in the water pipes of your house can make them knock, ping and make strange noises, bubbles cause uneven flow of fluids which disrupts, or even blocks, the delivery of oxygen in the bloodstream. An arterial gas embolism can block blood flow leading to death by heart attack or stroke.


The speed at which treatment is required depends on the severity of the symptoms. Giving a person oxygen immediately is a good first step. The only real effective treatment is to get the person suffering DCS into a hyperbaric chamber. By increasing the pressure again it causes the gas bubbles to disperse into smaller ones that can more easily be cleared of the system slowly over time just by normal breathing. These facilities are rarely close by in such emergencies so rushing the patient to one is a time sensitive necessity. Ironically, flying a person subjects them to even lower ambient air pressure the higher the aircraft goes into the sky. This can exacerbate the condition, at least temporarily for the duration of the flight. Still the speed of getting treatment outweighs the risks and if medevac is the fastest option then that is the preferred method. Even so the aircraft may attempt to fly lower than usual if possible.

Additional Information

    : Lawrence Martin (Divers Alert Network) (MedScape)

Article by Michael Troyan. Michael has spent 20 years teaching non-majors biology and microbiology and currently works as an online instructor at Penn State University. He can be reached at mbt102@psu.edu. Michael is a frequent contributor to Ricochet Science, and this work was prepared to support the recent release of our Human Biology textbook.

What Is Scuba Diving – Everything You Need To Know

What Is Scuba Diving - Everything You Need To Know

Scuba diving is one of those activities that everyone says they want to do one day, but often never get the chance to experience. If you’re reading this right now, you are one of the lucky ones attempting to put their money where their mouths are and give scuba diving a try to explore the underwater world to explore unbelievable dive sites. But before you dive into deep waters or off dive boats, we must cover the basics of what recreational scuba diving is and how you can do it.

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There are many ways to describe scuba diving. Some people think of it as a sport or lifestyle while others think of it as a tourism activity or a meditative experience. In general, you may think of scuba diving as an underwater experience. At its core, scuba diving is an activity where you dive underwater to experience the beauty and nature that lie beneath the ocean.

There are various aspects and sub-branches of what scuba diving entails. However, in this article, we will keep things simple, short, and easy to follow and tell you about recreational scuba diving. We will talk about the basics you need to know about scuba diving as a beginner. So, if you are new to the world of scuba diving, keep reading so that we can dive into all you need to know to get started.

Scuba Diving along a coral reef

What Is Scuba Diving?

Scuba is a term that almost everyone has heard of. It is actually an acronym that stands for Self-Contained Underwater Breathing Apparatus.

Scuba diving as a sport is when a person dives underwater to explore the ocean. There are various types of scuba diving. However, for most people, scuba diving is an activity they do recreationally as tourists while on vacation or holiday. Recreational scuba diving often is done off dive boats to experience unbelievable dive sites. Recreational divers put on a scuba tank to breathe underwater to see the beauty of the ocean and interact with sea creatures.

Scuba diving is a common hobby among people of all ages. You may have heard how some people do yoga or Zumba to de-stress. Becoming a certified diver and going Scuba diving has become another meditative activity that many general people do to destress. The experience of being weightless and “flying” through the water while watching marine life, exploring spectacular reefs, underwater caves, or even diving into sunken wrecks is something unlike anything else in this world.

Many people also progress from being recreational divers to making scuba diving a profession or lifestyle. There are multiple types of professional Scuba diving careers including becoming a dive instructor or even a marine biologist or archaeologist to help with underwater research. As of yet, 80% of the ocean around the globe is still unmapped, and becoming a professional scuba diver allows you to help advance your knowledge of the underwater world.

Scuba Diving in the ocean

Is Recreational Scuba Diving Dangerous?

There are certain risks to scuba diving but ultimately it’s a very safe sport to enjoy. Millions of recreational divers go diving every year and there are very few accidents.

The primary rule any certified diver learns is to never dive alone. Always dive with a buddy, not only for safety but it’s always better to share the experience of experiencing unbelievable dive sites together.

You should research how to become a certified diver with a comprehensive diving program like PADI, NAUI, SSI, or BSAC. You should also research your scuba instructor, your dive school, and any dive locations you want to dive. Ultimately being prepared will make you a better diver.

If you are scuba diving as a tourist, there is very little risk involved. Recreational divers usually only travel in the safer parts of the ocean. Additionally, you will have an instructor or experienced divers (called divemasters) who will teach you everything you need to know before diving. You will not be allowed to go diving off dive boats or experience marine life on dive sites until you prove that you know all the basic moves and safety signals.

In the end, you are immersing yourself in an unbreathable liquid using equipment for life support and diving in an environment where wild creatures inhabit so like any activity you need to be a properly certified diver and respect the underwater world.

Instructor and students during scuba diving lessons

Do You Need A Certification To Scuba Dive?

Technically, it is not illegal to scuba dive without a certification. However, if you want to scuba dive safely, you will need to get certified by a scuba diving instructor. As previously mentioned. If you are recreational diving, you will need to train under an instructor. The instructor will give you lessons just like a regular class.

After the lessons, you will have to prove your knowledge by taking a test. If you pass the test, you will be certified as a beginner scuba diver. Almost every institution around the world will need you to show your license or certification before letting you dive into their premises or onto their dive boats. So, if you want to scuba dive properly, you need to have a scuba diving license.

In general, scuba diving isn’t something you can learn on your own. Even if you learn the principles of everything online, putting them to practice is a whole other issue. Thus, if you want to learn scuba diving properly, and get access to a wider territory, getting a scuba diving license is essential.

Learning to Scuba Dive in a Swimming Pool

How To Get A Scuba Diving Certification?

To get a scuba diving certification, you need to enroll in a scuba diving class. Various agencies around the world offer scuba diving courses. If you complete these courses with positive results, you will receive a scuba diving certification. Some of the most popular scuba diving agencies include PADI, BSAC, SDI, NAUI, etc.

However, before getting a scuba diving certification you have to make sure you meet the physical requirements. In most places in the world, you have to be at least 12 years old to get scuba diving lessons – although there are some taster or discovery dive programs with most agencies starting from 8 years old.

You also cannot apply for a scuba diving certification if you have medical issues. Before starting any certification course, you need to fill out a medical form that declares you fit for diving, assuming you are. If you have some type of medical condition, you will need your doctor to sign off on it.

Aside from medical issues, almost anyone can enroll in scuba diving lessons. There are even special organizations that help disabled people learn how to scuba dive. Additionally, scuba diving certifications do not have any expiration dates. So, if you are certified once, you are certified for life. However, it is good to brush up on skills if you haven’t dived in a while as although it is like riding a bike it’s always better to get your skills refreshed.

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Scuba diving at Yonaguni In Japan

What To Expect From Scuba Diving Lessons?

Scuba diving lessons are pretty simple and uncomplicated. For recreational diving, you can receive a beginner’s certification – like PADI Open Water – in three to four days after completing the lessons often taught at the dive shop. If you are traveling you can do something called a “referral” where you complete your theory training and exam online or via a local dive shop, then you do your pool training and open water dives at your destination.

However, in more advanced courses, it can take four to six months for you to receive a scuba diving certification. Since the skills taught in advanced courses are more difficult, it takes longer to get certified.

In a beginner’s scuba diving class, you will learn the basics of scuba diving. Most of your lessons will be about planning your dive, and using your underwater breathing apparatus and other equipment properly. You will also learn the techniques, procedures, and safety drills for simple dives as well as basic underwater hand gestures. Additionally, you will also receive some physical training by diving in a swimming pool or shallow waters.

A beginner’s scuba diving class won’t complicate things with technical jargon. The main focus will be on safety protocols. For instance, what to do if you run out of air, and how to control your buoyancy in the water. Or, how to tell your instructor that you need help. So, if you’re a beginner diver, rest assured that the initial courses will be easy and guarantee your safety.

Scuba diver showing an OK hand signal

Tips for Staying Safe while Scuba Diving

Here are some tips that can help you enjoy your dives while staying safe while scuba diving.

  • Ensure that all components of your diving equipment are in good working condition before you embark on a dive. If you discover any problem with the equipment, don’t use it and inform your instructor immediately. Any scuba equipment that has been tampered with or is faulty should not be used for scuba diving.
  • Never hold your breath underwater while diving because many people instinctively do this. Even if you are an experienced diver, you could get into trouble if you hold your breath underwater.
  • Diving more than 30m/100ft below sea level can cause the nitrogen in the air to affect your body, because of which you might experience a ‘bends’ situation where nitrogen bubbles start appearing in your blood and joints. This is a serious condition that requires immediate medical attention.
  • Never go on a dive if you feel sick, have a fever or a cold. Many people often ignore their symptoms and end up going scuba diving, but this is a very dangerous thing to do as it can lead to further complications such as a ruptured eardrum.
  • Never panic underwater because this will only make the situation much worse. Panicking is common among untrained divers who are trying to ascend too quickly.
  • Don’t dive alone if you are not an experienced scuba diver because there might be problems that you may not deal with on your own. So, diving should always be done during a buddy dive or in pair of divers.
  • Never go on a night dive without proper training because it is very dangerous, and you could lose your way in the dark if you are not adequately equipped with navigation gears.

How to Get Started With Scuba Diving

People of all ages and sizes may learn to scuba dive safely due to technological developments in diving equipment, medicine, and training. scuba diving is possible for the majority of individuals who have a basic level of physical fitness and feel comfortable in the water.

Choose a Scuba Diving Course

Different diving courses are available like open water certification, advanced open water certification, rescue diver courses, etc. These can be completed by anyone ready to take up the challenge. Even people with no previous experience in scuba can undertake these certifications and become certified divers within a short period.

Buy or Rent Dive Gear

You can rent or buy equipment, which makes it more feasible for your budget.

Enroll in a Scuba Diving Course

Typically, this type of training is conducted in groups, but you can go in solo if you prefer—several scuba diving certification organizations to choose from like PADI , NAUI , BSAC , etc.

Learn Essential Dive Theory

Theory classes teach you about diving equipment, physiology, decompression calculations, and dives. You will also learn to deal with dive emergencies like running low on air or getting lost underwater.

Practice Simple Skills With an Instructor

You can practice beginner skills with an instructor to get a good grip on the basics. You need to pass a few simple tests before going in for your first scuba dive.

Go On Your First Dive

Your first-ever dive is something that you will never forget! After passing all the tests, you will go for a drive along with your instructor. Several scuba diving certification agencies ensure that you get the most out of your time and money invested in this course.

You will be certified as an open water diver when completed the training process

Are you ready to become a Scuba Diver and explore the underwater world?

Scuba diving is a fun activity that can help you destress and momentarily escape from your mundane life. Though there are minor risks involved, they can be easily overcome through proper training and getting a scuba diving certification.

We hope this article helped you learn the basics of scuba diving. Now that you know the fundamentals, we hope you will continue your journey and give scuba diving a try.

Source https://www.uw360.asia/what-happens-scuba-dive-tsunami/

Source https://ricochetscience.com/what-happens-to-your-body-when-you-scuba-dive/

Source https://www.deeperblue.com/what-is-scuba-diving/

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