All freedivers should be aware of and mitigate against surface blackouts. With good technique and regular practice you can reduce your risk but never eliminate it. Always follow the safety rules on not diving alone and make sure you are accompanied by an experienced diving buddy who knows how to handle freediving blackouts.
Freedivers may blackout at the surface due to a lack of oxygen because of hyperventilation before diving, pressure reduction affecting oxygen supply on ascent, or a combination of factors. Blacking out at the surface is a risk that freedivers always need to bear in mind and one of the key reasons why freediving should always be undertaken with a diving buddy rather than alone.
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If you’ve experienced, witnessed or read about freedivers blacking out at the surface, you might be wondering why it happens and what causes it. Our article tells you more about surface blackouts in freediving, how to mitigate the risk and how to rescue someone who has blacked out while freediving.
What causes divers to blackout?
There are a number of different types of freediving blackout, all caused by a lack of oxygen supply to the brain (hypoxia), but occurring at different stages of a dive and having slightly different mechanisms.
Blacking out at the surface is caused by low oxygen (hypoxia) to the brain towards the end of a breath-hold, when the swimmer does not necessarily experience a sufficiently urgent need to breathe and has no other obvious medical condition.
Surface blackout triggers might be hyperventilation just before a dive, pressure reduction on ascent, or a combination of these factors. While inexperience raises the risk, victims also include established freedivers without previous problems.
What happens if you pass out underwater?
A freediver who passes out underwater will reflexively inhale, taking water into the lungs. If they are wearing a snorkel and have kept the breathing tube in their mouth (against safety guidelines), their lungs will flood directly with water as their tongue relaxes. Without quick assistance, the freediver is likely to drown.
This is a big danger within the sport of freediving, and it’s why you should always dive with a buddy. Even the very best freedivers can get into trouble underwater, as detailed in our Truth Behind Freediving Deaths (opens new tab) article.
How do I stop freediving blackouts?
There are behaviors and practices which increase the risk of occurrence, injury or death from shallow water or surface black out in freediving and these should be avoided in order to mitigate risks. They include:
Hyperventilation: carbon dioxide concentrations trigger the urge to inhale. Over-breathing before descending can lower a freediver’s carbon dioxide levels to the point where the urge to breath is impaired and the diver cannot judge their ascent in time to avoid hypoxia.
Diving beyond your competence: you will be at risk of blackout if you try to dive deeply or for a long period without haven’t put in significant training and practice. Over time, these will make your body more efficient in using oxygen and more tolerant of working hard under apnea conditions, enabling longer, safer dives.
Over-weighting: if a freediver experiences a shallow water blackout, they will sink if they are negatively buoyant. For this reason, you should choose weights which leave you positively buoyant during the last 10 meters of ascent. At this depth it will be easier for your diving buddy to rescue you and provide emergency care if you black out.
Freediving alone: without a freediving buddy on hand, there is no realistic prospect of help if you experience shallow water blackout in open water, and you will probably die. If a freediving buddy dives down to join you for the last ten meters of a dive, they will be on hand to react quickly in case of blackout.
Poor preparation: Hunger, dehydration, hypothermia and stress can all increase blackout risk. Make sure that you’re well fed, hydrated, rested and calm before beginning a freediving session.
How do you rescue a blackout?
Speed is essential in rescuing a freediver who has experienced a blackout. If acting as a diving buddy, make sure you monitor the diver closely over the last ten meters or so of their dive, remaining close enough to grab hold of them if they lose consciousness. In the case of blackout, you should take the following steps as quickly as possible.
1. Surfacing
Bring the unconscious freediver to the surface with their airways closed and mask still on. While there are several recommended holds for maneuvering the diver, time is more important if necessary you should grab any part you can and pull them up. If they’re so heavily weighted that you cannot get them to the surface, remove their weights, and possibly your own. Once at the surface, keep them there.
2. Activate the breathing response
Clear the face by removing any mask, googles, nose clip, or other accessories, and then blow on their skin, tap on their face or shoulder and/or talk to them. Even if their eyes are closed their hearing my still be functioning, and touch receptors on the skin are very sensitive to temperature and pressure. These actions may be enough to trigger the breathing response.
3. Rescue breaths
If the freediver does not respond to touch or sound after 15 seconds, give them two full mouth-to-nose rescue breaths. (These can be more effective than mouth to mouth in this situation due to possible spasm of the larynx, and difficulty of effecting a firm seal between mouths.)
4. CPR
If the diver does not recover within a minute after your rescue breaths, you must tow them to a boat, shore, or other hard surface, while keeping their head out of the water. Pause and give more rescue breaths as you swim (perhaps two breaths for every eight strokes).
Once out of the water begin CPR and ask someone to contact emergency services. Give chest compressions and rescue breaths to the diver until medical assistance arrives.