What Happens During Freediving Blackouts?
One of the more intimidating aspects of freediving is the risk of a blackout. While it may sound frightening, understanding what happens during a blackout can help you stay safe, make informed decisions, and maintain respect for the ocean and your limits.
In this blog post, we’ll explore the physiological mechanisms behind freediving blackouts, why they happen, and how our bodies are equipped to handle these moments.
The Science Behind Freediving Blackouts
A blackout, or loss of consciousness during freediving, occurs when the brain doesn’t receive enough oxygen. It’s usually caused by hypoxia, a state of low oxygen in the body, often as you ascend to the surface after a dive.
The Role of the Mammalian Dive Reflex
When you dive underwater, your body activates the mammalian dive reflex (MDR), a survival mechanism shared with marine mammals like seals and whales. The MDR slows your heart rate, restricts blood flow to your extremities, and prioritizes oxygen delivery to vital organs like your brain and heart.
This remarkable reflex helps prolong your breath-hold, but as your oxygen levels drop, your brain can eventually reach a point where it cannot function properly—leading to a blackout.
👉 Related Read: “Freediving and the Mammalian Dive Reflex: Nature’s Safety Net”
Why Do Blackouts Happen at the Surface?
Most freediving blackouts occur during the ascent or immediately upon surfacing. Here’s why:
1. Partial Pressure of Oxygen:
At depth, the increased pressure of the water compresses the gases in your body. This means oxygen remains more readily available to your brain and muscles. But as you ascend, the pressure decreases, and the oxygen partial pressure drops. This rapid decrease can result in a blackout just before or after you break the surface.
2. Hyperventilation:
Breathing too quickly or deeply before a dive reduces the CO2 in your blood. While this might feel like it’s giving you more breath-hold time, it can delay your urge to breathe without increasing your oxygen reserves. This can trick your body into ignoring critical low oxygen levels, increasing blackout risk.
What Does a Freediving Blackout Feel Like?
Surprisingly, many freedivers report that a blackout feels calm. There’s no panic or pain because the brain shuts down before it can process distress signals. The experience can be akin to falling asleep—peaceful, yet dangerous without a buddy present.
How Your Body Responds During a Blackout
Even during a blackout, your body doesn’t give up on protecting you.
• Loss of Consciousness:
This is your body’s way of conserving oxygen. By shutting down higher cognitive functions, the brain reduces oxygen demand to focus on essential processes.
• Laryngospasm Reflex:
When you lose consciousness underwater, your body triggers a laryngospasm—a temporary closure of the vocal cords. This prevents water from entering your lungs, giving your buddy critical time to bring you to the surface.
👉 Resource: Learn more about hypoxia and the body’s protective mechanisms in this study on hypoxic tolerance.
How to Prevent a Freediving Blackout
While the body has protective mechanisms, prevention is the ultimate safety strategy.
1. Never Dive Alone
Always freedive with a trained buddy who understands rescue techniques.
2. Focus on Proper Breathing
Avoid hyperventilation and practice controlled breathwork to build your CO2 tolerance.
👉 Related Read: “Breathwork Techniques for Anxiety and Freediving”
3. Progress Gradually
Depth and duration come with time and consistent training. Don’t rush your progress.
4. Be Aware of Warning Signs
Dizziness, tingling, or an overwhelming urge to breathe can indicate you’re approaching hypoxia. Listen to your body.
Recovering from a Blackout
If you or a buddy experiences a blackout, the most important thing is quick action:
1. Surface Support:
Bring the diver’s face above water, take your recovery breaths and then call them by their name, tell them to breathe, remove their mask, blow in their faces. If none of this makes them respond, then start mouth to mouth resuscitation.
2. Rescue Breaths:
When the diver is conscious and breathing, stimulate breathing by telling them to breathe and to stay awake. Support their body to make sure their airways are above water. Take them to the closest floating device (buoy, boat).
3. Recovery Breathing:
Once the diver regains consciousness, encourage them to breathe deeply and calmly to reoxygenate their body. Take them safely to land.
👉 Resource: Check out this medical guide on basic life support techniques for hypoxia.
The Takeaway
Freediving blackouts can sound intimidating, but understanding their causes and your body’s response can help demystify them. Armed with proper training, safety protocols, and respect for your limits, freediving remains a safe and awe-inspiring activity.
Freediving is a balance of mental and physical mastery, and while the risks are real, they’re manageable. Always dive smart, prioritize safety, and trust in your training.
Happy and safe diving!