Freediving blackout

Freediving and blackout: the danger of losing consciousness underwater

Freediving is one of the most thrilling yet dangerous underwater sports. The main hazard is the risk of a blackout, a loss of consciousness that can have serious health consequences and can even be life-threatening. Let's look in more detail at what this process entails, why it happens, and what can be done to prevent it.

What is a blackout?

In the context of freediving, a blackout is a moment when a person loses consciousness underwater while their heart continues to beat. This phenomenon is often seen as the body's last line of defense against death when the oxygen level in the blood critically drops.

Physiological mechanisms

When a free diver holds their breath and dives, the so-called diving reflex is activated. This set of physiological changes includes slowing down the heart rate, reducing metabolism, and redistributing blood flow to vital organs. When the oxygen level in the blood drops to a dangerously low level, the body turns off its most energy-consuming component - consciousness. This is a blackout.

Protective mechanism: laryngospasm

Interestingly, during a blackout, a person experiences laryngospasm - a spasm of the vocal cords that prevents water from entering the lungs. This spasm can last from 30 to 180 seconds and gives time for a buddy to pull the victim out of the water and provide first aid.

Signs of an impending blackout

It is important to recognize the symptoms leading up to a blackout to prevent potentially dangerous situations underwater. Below are symptoms to watch out for:

  • Ringing in the ears. It may manifest as ringing, buzzing, or hissing that gradually intensifies and drowns out all external sounds. This can be the first warning sign of impending hypoxia.
  • A sensation of warmth. Some divers describe this as feeling as if they are covered by a very warm blanket, starting from the neck and the back of the head, gradually spreading throughout the body.
  • A tingling sensation. Some free divers report a sensation as if ants are crawling on their fingers, hands, and then throughout the body. This is likely caused by the preceding rush of warmth throughout the body.
  • Diving begins to seem easier. If diving was difficult and suddenly becomes easier, this may be a sign that the brain is no longer functioning normally and you are approaching the limits of your hypoxic tolerance.
  • Narrowing of the field of vision (tunnel vision). Vision begins to narrow as if you were looking through a tunnel until only a small area remains in front of you, or vision may disappear completely.
  • Confusion. This symptom is closely related to the feeling of ease during the dive - you no longer think clearly and find it difficult to concentrate.

Actions when symptoms appear

If you experience any of these symptoms while diving in a pool, you need to surface immediately. When diving in open waters, you should immediately signal your buddy about your condition and move towards the surface without rushing. In recreational freediving, you should never approach a state of hypoxia. The appearance of any of these symptoms is an unacceptable practice for the safety of the freediver.

Signs of trouble

When freediving, it is essential to closely monitor your partner's condition. Pay attention to the following signs:

  • Change in swimming style: if the movements of a usually strong and confident swimmer have become sluggish, it may indicate hypoxia.
  • Vacant gaze: if the gaze of a freediver rising from the depths seems absent and they look through you, this is a serious symptom of potential problems.
  • Uncontrolled grabbing of the rope: attempts to grab the rope haphazardly can be a sign of distress, unlike conscious holding of the rope during leg cramps.
  • Acceleration at the end of the dive: if a diver accelerates before surfacing, it may indicate an attempt to deal with the accumulation of carbon dioxide and the desire to breathe air as soon as possible, which is a sign of losing control.
  • Exhaling underwater: a visible exhalation of bubbles underwater is not normal and may indicate oxygen depletion and the threat of fainting.
  • Inability to keep the head above water after surfacing: this is a clear symptom of oxygen starvation, as well as uncontrollable twitching or reduced responsiveness.

Any anomalies in the swimmer's behavior: if you notice any unusual changes that cause you concern, your intuition is likely correct, and you should take the necessary actions to provide assistance.

Prevention and safety measures

The risk factors for a blackout during freediving are diverse, and it is important to consider them to ensure a safe dive:

  • Fatigue and stress: Maintaining mental and physical calm before diving is essential for conserving energy and oxygen. Tension and stress can provoke a sense of panic, which is a sign that you are already exceeding your limits. In such a state, diving should be postponed or diving goals should be modified.
  • Diving technique: Proper execution of freediving techniques learned in AIDA courses reduces the effort required to move underwater, which increases safety.
  • Recovery breathing: Always perform recovery breathing, making it a habit after each dive. This helps your body automatically respond in emergencies.
  • Hydration: Maintaining the body's water balance is crucial. Fluid loss can occur due to the wetsuit, pressure changes on the kidneys, and high environmental temperatures. Attention should be paid to regular fluid replenishment during and after dives. Read more about this in the article "Improving performance in freediving: the importance of hydration."
  • Diving with a buddy: Diving should always be done with a partner who is trained and ready to assist. Diving without a buddy is unacceptable and increases risks.
  • Proper weighting: Correct weight adjustment reduces the effort required for diving and increases safety, especially in an emergency.
  • Use of a buoy, rope, and lanyard: Using a buoy in freediving provides visibility of the diver on the surface and is a place to rest between dives. The rope and lanyard not only increase safety by making it easy to find the way back to the surface but also prevent the risk of disorientation underwater. Moreover, in deep dives or conditions of poor visibility, the lanyard serves as an important means to maintain contact with a buddy and the buoy.


In summary, it should be stated with full responsibility: there are no advantages to losing consciousness during freediving. The belief that training on the edge of possibilities leads to outstanding results is mistaken. Holding your breath to critically low oxygen levels in the blood can be associated with an increased risk of brain cell death, even if there is no complete loss of consciousness. Harmful effects on the brain, whether from sports exercises, alcohol intoxication, or even a common sneeze, have a cumulative effect, and frequent blackouts carry serious health risks.

In addition, after recovering from fainting, a freediver may be disoriented and behave inadequately. It is very important to continue monitoring such an athlete after a blackout until it becomes absolutely clear that they have fully recovered and regained control of their cognitive processes and body.

Do not exceed your limits and dive for pleasure, and our Apnetica Freediving school will help make your sessions not only safe but also interesting!

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