While spearfishing there is one medical condition that can occur with disastrous results and claims a large number of lives each year...Blackouts.
Blackouts while diving are usually caused by a lack of oxygen. Statistics show that a spearfisher’s greatest danger or risk is a shallow water blackout. Shallow water blackouts are without a doubt responsible for far more spearfishing deaths than shark attacks, even if JAWS had you believing otherwise. Shallow water blackouts are actually a bigger danger to spearfishers than all other diving hazards combined. Deaths from shallow water blackouts also seem to effect spearfishers more than other divers, as spearfishers often like to hunt alone or find themselves separated from their partner.
Shallow Water Blackout Prevention.
To protect yourself from shallow water blackouts whilst spearfishing or scuba diving it’s important to first understand what causes you to blackout in the first place. Shallow water blackouts occur near the surface of the water, hence the name, as the largest pressure change when diving happens within the top 10m of water.
When you first descend into the water, your lungs are full of air which has around 20% oxygen in it. As you get deeper the increased pressure quickly reduces the size of the gas, in turn concentrating the oxygen particles. This can be a problem as after spearfishing for hours you will have used up most of the oxygen in the gas and when you return to the surface, the gas will double in size however the oxygen content will be much lower causing you to blackout.
In the vast majority of cases the change in pressure found within the top 10 metres of the surface is not a problem, however if you have used too much oxygen while spearfishing you will likely blackout. Without a dive buddy or partner there to help it is very unlikely you will survive a shallow water blackout which is why it is such a deadly silent killer.
Another dangerous medical condition associated with spearfishing is hyperventilation, which is another major cause for blackouts whilst scuba diving. When hyperventilating you breathe in more oxygen than the body needs. Some divers hyperventilate before a dive to try and get more oxygen into their body, however this is merely a false hope and is actually dangerous.
In day to day life the oxygen level in your blood is around 97%, therefore it is quite easy to get this up to 100%, in fact as few as 3 or 4 deep breaths will do the job. When you hyperventilate before a dive you reach 100% saturation very quickly and if you continue to force oxygen into your body the CO2 level in your blood will drop to a dangerously low level.
CO2 in the blood is actually what triggers breathing and the urge to breathe is actually CO2 triggered. When you hyperventilate it disrupts the body’s natural trigger by artificially dropping your CO2 level.
This can prove fatal if you are distracted by fish or your surroundings and are then suddenly compelled by an intense urge to breathe which can cause problems as you ascend through the shallow water blackout danger zone.
Long story short...DON’T HYPERVENTILATE!