Freediving is a very safe and healthy sport when diving well within your limits. If you are a beginner learning to freedive, chances are you won't be doing super long and deep dives - just duck diving down to the reef and back up again. This sort of freediving has minimal safety risks. However, if you start to do longer and deeper dives, its important to be aware of risks and safety considerations.
One of our resident expert freedive instructors Wayne Judge has compiled a list of safety considerations below. If you have any further questions about freediving, pop in-store for a chat or consider one of our freediving courses.
Can I freedive alone?
There is an unwritten law amongst all freedivers, NEVER FREEDIVE ALONE. This applies to all freediving activities, especially those in the ocean. Unwritten, as it doesn’t exist as a law, but divers ignore it at their own peril. If there was one safety action that is such a basic that it will handle nearly all other lapses of safety, this is it. But it is not enough that one enters the water with a dive buddy, the responsible freediver must watch his buddy as he dives and recovers, and must expect the same care.
Should I breathe up before a freedive?
Despite the loud decrying of hyperventilation, the breathe-up is still a largely misunderstood action and we still have people hyperventilating before leaving the surface. The definition of hyperventilation is simply, breathing more than the current activity level of the body demands.
It is important to understand that the operation level of oxygen saturation in the blood is usually around 96 -98%. In most cases a single deep breath would take it to 100%. After the blood is fully oxygen saturated, continued breathing does nothing more than rid the body of carbon dioxide. The continued breathing will not give you longer dives before blackout, and in fact it will shorten your dive time.
You may then ask, why do divers hyperventilate when the result will allow them to blackout sooner. Divers are led to believe that they have a longer breathhold when they hyperventilate because it makes them more comfortable and there is a delay in experiencing the urge to breath. It is the carbon dioxide level in the blood that triggers diver’s the urge to breathe.
It is not the low oxygen. It is a simple process. When a person exercises it burns oxygen and this creates carbon dioxide as a waste product. This CO2 is usually exhaled and more oxygen rich air is inhaled. When a diver holds his breath and does not exhale, exercise causes the CO2 level to increase and the diver will get the urge to breathe. The urge will start low but can quickly escalate to the point where the diver is experiencing involuntary contractions of the chest and considerable discomfort. The practice of hyperventilation, by expelling CO2 delays the onset of the urge to breathe without giving any more oxygen. This can encourage the diver to overstay his time and not leave enough oxygen to return to the surface, and he blacks out. Hyperventilation is a major cause of blackouts.
The accepted guideline promoted since the dangers of hyperventilation were discovered, was no more than 3 - 4 deep breaths before diving. The multiple deep breaths and purges of CO2 practiced in the past should not be done.
It is a common practice amongst top level freedivers to do no increased breathing before an event. This is an effective way to produce a big performance utilising the body’s natural reactions to high levels of CO2. It works as follows:
- The freediver tidal breaths before the event. (normal shallow breathing)
- The diver takes one deep breath and starts his event.
- Because he has not purged any significant amount of CO2, the CO2 levels rise fast.
- High CO2 levels cause the blood to become more acid than alkaline.
- The haemoglobin (protein molecule that carries oxygen) release greater amounts oxygen when the blood is more acidic.
This is the Bohr Effect in operation. https://en.wikipedia.org/wiki/Bohr_effect.
This helps the freediver by ensuring all the oxygen held by the haemoglobin is released giving the best performance possible. Through the nature of the Bohr Effect the oxygen is released exactly at the points in the body where it is needed. Because the levels of CO2 are not low from hyperventilating the diver has a faster onset of the MDR meaning he has more of his performance done with higher O2 economy, with the heart rate lower, vascular constriction (blood restricted to the extremities) and more haemoglobin in the blood.
This increase of performance comes at a price. Along with the onset of the MRD comes the urge to breathe and related mental effects. In such a breathe-up the freediver has much more of his swim done under these stressful conditions. It usually takes some dedicated training to enable a diver to move through these effects and not give up on the dive. This is especially prevalent in the pool disciplines where the freediver is such a short distance from the surface and relief. Dives prepared with this method often are accompanied by higher lactic acid production. This is covered in the referenced material above on the Bohr Effect. The high lactic acid creates a burning sensation and pain in the muscles being used, and in severe cases inhibits the muscle activity. Advanced freedivers will focus much of their training to get more in control of these situations so the benefits of the Bohr Effect can be taken advantage of.
As a note, it is a tragedy of divers who have blacked out after hyperventilating, that there was more oxygen available in the blood, unreleased by the haemoglobin due to the lower CO2 levels.
A blackout while freediving is simply a loss of consciousness from low oxygen. It can happen in shallow water, deep water, swimming pools and even the bath. It is a blackout from holding the breath longer than the freediver has oxygen to maintain consciousness.
Shallow Water Blackout
A shallow water blackout is a loss of consciousness from lack of oxygen. It is called a shallow water blackout because it happens in the shallow section of the dive. A shallow water blackout happens at the end of a dive when the freediver is surfacing and is moving into lower water pressure. In the final 10 metres the water pressure change is so drastic, that the air in the lungs doubles in size, this means the pressure halves. In the situation where where the oxygen level in the lungs is already depleted this change of pressure has the result of starving the brain for oxygen rendering the diver unconscious. Full details are available in the freediving courses available.
If my dive buddy blacks out, what should I do?
The best thing to do is to become trained before you ever have to handle an unconscious diver. You will get this training in freediving courses. Freediving clubs affiliated with the Australian Freediving Association train their freedivers in these actions and regularly drill them.
The basics are:
- Get the divers airways out of the water and keep them out.
- Removed the diver’s mask
- If he is still holding his breath, encourage the diver to breath. Say his name and tell him to breathe until he does.
- Lightly tap or rub his face, to bring his attention back to his environment.
- Blow air on his face, to stimulate the facial nerves which encourages him to breathe.
- If he hasn’t taken a breath it is probable that his windpipe is spasmed close. A safety breath should be delivered, as in mouth to mouth with the purpose of unlocking the spasmed muscles.
- If he hasn’t regain consciousness, there is most likely some other problem. The freediver should be returned to the boat/shore and full first aid emergency procedures carried out.
The smart and responsible thing to do is get trained and drilled to handle this emergency.
What is a lung squeeze?
A lung squeeze is the rupture of lung tissue during a dive. It occurs when the pressure of the surrounding water compresses the lungs putting the tissue under stress. When the pressure becomes too much the tissue is damaged and bleeding occurs. A trachea squeeze has the same cause but the damage occurs in the trachea instead of the lungs.
It was thought by many that a lung squeeze could only happen when the diver reached depths where the lung volume is reduced to less than the diver’s residual volume creating a negative pressure. This is not the case. A recent survey of spearfishers by Noob Spearo found 13.2% of participating divers had experienced a lung squeeze and it is very unlikely that any of their dives had them in the depth where their lung full was below residual volume. http://www.noobspearo.com/the-vault-blog/lung-and-trachea-squeeze-survey-results/
Not all freedivers get lung or trachea squeezes. For some it is a rare or even a once only occurrence. There are some freedivers for whom lung squeezes are regular and these often go unreported. An investigation into a freediving death from a massive lung barotrauma found the diver had a history of lung squeezes and had increased his depth at a rapid rate for a new diver. This has brought the spotlight onto this area and has highlighted the importance of handling the subject of lung and trachea squeezes thoroughly and safely.
How can I avoid a lung squeeze?
Lung squeezes can be brought about through actions by the diver, conditions existing in his body, or a failure to consider the diving conditions. Here is a summary of the more well known causes and handlings.
- A freediver can advance too fast in depth diving, not giving the body enough time to attain the needed flexibility. As the pressure increases and the volume of air is reduced in the lungs, this creates the stress on the lung tissue. If the diver’s thorax and organs have not become accustomed to this though gradual increases of depth, or if the diver has not spent enough time and energy on attaining flexibility he could develop a squeeze. The handling for his is to gradually increase one’s depth over a longer period of time, with no big increases. It is wise to only increase a metre or two at a time. It is also a good practice to regularly stretch the core area. There are exercises designed for this, many originating from yoga breathing practices. The diver should find a freediving instructor who also has a successful record in depth diving as a coach or mentor.
- Many lung squeezes have come from the actual moment the freediver experiences a strong contraction at depth. When the lungs are under considerable stress, the automatic chest contraction as the body demands air is enough to tear the tissue. The handling for this is to do a thorough breath holding warm up prior to a deep dive. Such a warm up can extend the time before the freediver gets a strong contraction and/or make the contractions less intense. Warm up dives usually consist of shallower dives done before the main one. Some do these as FRC to bring about faster results. Negative warm-up dives can be risky as they approximate the conditions of a deep dive and can also bring on strong contractions. Some experienced freedivers managed to forestall or reduce the intensity of contractions just by consciously taking over control of the muscles involved.
- Physical activity at depth, especially involving the core area has often caused squeezes. With the lung tissue under stress the diver reaches, bends, twists or carries out some such exercise that increases this stress. The turn at the bottom of the dive rope could be such an exercise if it were not done correctly. Even looking up is enough to precipitate a trachea squeeze. Spearfishers have developed squeezes from pulling fish from caves in depth. The handling is to knowingly reduce the above type of movement as you get deeper. A squeeze could keep you out of the water for weeks, so it pays to discipline your movements to avoid them.
- A temperature change in diving conditions when not given sufficient attention can bring about a squeeze. A great example for Australian freedivers, happens once a year when they attend New Zealand’s national depth competition held in the chilly waters of Lake Taupo. Divers used to tropical waters can be shocked when they find the 8 degree water often encountered in Taupo. The initial reaction is to tense the body as an effort to counter the cold. When they should be relaxing the core muscles to enable the body-flex to absorb the pressure increase, they tense up. This increases the amount of stress brought to bear on the lung tissue and hence the squeeze. The cold waters of the deeper sections of even Queensland’s Lake Eacham can bring about the same conditions. There are also areas in the Mediterranean Sea notorious for having a cold layer of water at depth. (thermocline) Contractions in cold water are usually far more intense leading to even increased risks. The handling is in the diver’s preparation. How cold is the water? Is there a thermocline? Have I got the right wetsuit for the conditions? How much of a warm up is necessary? Are examples of questions that should be asked.
- The mental and physical condition of the diver have a great bearing on a freedivers likelihood of sustaining a lung squeeze. A freediver who has not trained enough for a competition or a training level of diving he attempts, is at great risk. For example take a diver who has not done deep dives for some months then, at considerable cost, travels for a week at a world class dive site. Wanting to get the most out of this time it is easy for the freediver to try to advance too fast and attempt depths beyond the mental and physical preparation level. This is a risky scenario and freedivers with limited time need to consider this. A freediver attempting depths he/she is not mentally prepared for, or who has mental stress from other life situations can lead to dives done under anxious tension. This tension often transfers to the body leading to an increased risk of a squeeze. The handling for this is to plan diving preparation with this in mind. Write a plan that logically brings the performance up in a gentle gradient and then stick to the plan. Freediving competitions with a much higher level of stress and expectations can be the cause of lung or trachea squeezes, so sensible planning is much more important. Other life stresses can often disappear or become less important if you work on a real diving plan. Freediving has great mental benefits.
What should I do if I get a squeeze?
If a freediver develops a squeeze he/she should stop diving and get a medical check up. With correct handling, a small squeeze could heal in just a few weeks and the freediver could continue diving. However, unhandled, a small squeeze could become big and the diver could end up spending a long time out of the water. One diver incurred a small squeeze and because he continued diving despite only moderate depths, less than 40 metres, often with insufficient warm up, the squeeze kept recurring. This continued over a year. The squeeze although starting off very minor, worsened until it became quite a show of blood after each recurrence. It took some weeks out of the water, then he spend a whole year without diving below 20 metre to ensure it was fully healed.