So far it’s all been fun and games, and Freediving is great fun, but on a serious note, you must know how to deal with shallow water blackout if you’re going to continue to freedive. It may just save your life.

This isn’t a fun topic, but it’s one that you absolutely must know if you’re into freediving or spearfishing. Believe it or not, shallow water blackout occurs most commonly with experienced freedivers and strong swimmers.

In simple terms, shallow water blackout or hypoxic blackout is fainting or passing out underwater, usually occurring in the last meter or two before a freediver re-surfaces. IT’s caused due to a lack of oxygen in the brain caused by holding your breath for too long. And scarily, it occurs without any warning whatsoever, rather the opposite occurs where divers have been known to experience a euphoric state that actually encourages them to try hold their breath for longer, shortly before blacking out.

Understanding how hypoxic blackout occurs is critical to understanding how to prevent it. Overbreathing before diving down, or hyperventilating on the surface before freediving, causes the diver to lower their Co2 level in their body. This is usually done in an attempt to increase the divers breathhold time.

However as we discussed in a previous video, the urge to breathe isn’t caused by a lack of oxygen, but rather the urge to breathe is caused due to a build up of Co2 in our bodies. So If we have hyperventilated to reduce our Co2 level before diving underwater, we are actually eliminating our bodies urge to breathe. And if our body isn’t telling us that we need to breathe as we’ve hyperventialed, the diver can become oxygen starved without realising it, and can pass out or faint underwater.

Once the swimmer blacks out, the body will react and trigger a breath, however as the diver is underwater, the lung will fill with water and cause the diver to drown.

Now that we understand how it happens, preventing it should be fairly clear. The answer is to never Hyperventilate, and lower our Co2 level to a point where the treat of blacking out becomes a reality. As freedivers, you will need to breathe up, but you should never push this to a point where you are hyperventilating. Similarly, never ignore the urge to breathe and push your bodies limits too far.

Finally, we’ve stressed this repetitively throughout this series, but we must always dive with a buddy, and while diving, we must ensure that we are close to our buddy and that our buddy is alert and keeping an eye on us. If a shallow water blackout occurs, our buddy is likely the only person who will be able to save our life.

Hypoxic blackout is easy to identify. The diver will likely freeze, mid water and stop swimming, their limbs will become slack, their head may roll forwards onto their chest, the diver may convulse, and they may begin sinking.

If you find yourself in the unfortunate and unlikely circumstance where you buddy has blacked out, you should immediately get your buddy to the surface, remove their mask, and ensure that their head is held above the water at all times. It is likely that the diver will automatically resume breathing should their head be held above the surface. To assist the bodies reflex to resume breathing, you should also while holding their head above the water, blow on their forehead.

 If the diver does not resume breathing after a short period of time, this is where in-water resuscitation should begin, and you should get your buddy to shore asap where CPR can be properly conducted.

 Finally even once the diver has recovered, it is critical that they receive medical attention, as water may still be present in the respiratory system that can cause a secondary blackout up to 24 hours after the first event.

 Also remember, never scuba dive before freediving as this has been shown to greatly increase your chances of having a shallow water blackout. After scuba diving, leave at least 24 hours before freediving.

Freediving and spearfishing are leisure activities, but they’re also fairly extreme sports where we do push our body into unfarmiliar territory. Have fun underwater, but be sure to know how to deal with an accident should it occur.