Shallow water blackout (SWB) is caused by a lack of oxygen during a skin dive, often due to hyperventilation. Experts recommend relaxing before diving and resting between dives, as well as diving with a partner and following proper emergency procedures.
Shallow water blackout (SWB) is an unexpected loss of consciousness caused by a lack of oxygen during a skin dive. It can occur in an individual who free dives without the use of scuba equipment, or even in someone who is swimming underwater in a pool. Most often, SWB occurs because the diver hyperventilated prior to the dive. This can disable the body’s natural alarm system, which triggers the need to breathe before oxygen levels drop too low and the diver passes out.
Many divers and swimmers practice a technique called intentional hyperventilation, which temporarily suppresses the urge to breathe. This allows the diver to stay underwater for a longer period of time. This technique works because the urge to breathe comes from increased carbon dioxide levels in the body, not low oxygen levels. Hyperventilation removes more carbon dioxide from the body, so the pulse is not triggered as quickly. When the diver does not feel the need to breathe, however, he is much more likely to stay underwater too long and experience a shallow water blackout.
While some experts say intentional hyperventilation before a dive may be acceptable as long as only three or four breaths are taken, many others say the risk of excessive hyperventilation is too high. In fact, evidence suggests that hyperventilating before a dive does not significantly prolong dive time. Instead, experts recommend that swimmers and divers practice relaxing before diving, breathing normally and allowing the body to calibrate itself naturally. An excited diver can start breathing fast without realizing it, so it’s a good idea for new divers, especially to take a few minutes to calm down before diving.
It is also important for divers to rest a minute or two between skin dives so that the body can restore the oxygen level. Excessive exercise underwater should be avoided. When the need to breathe becomes urgent, the diver should be given access to air as soon as possible. A diver experiencing symptoms of fatigue or dizziness should stop diving immediately to avoid a shallow water blackout.
Divers should remember never to dive alone; people should always dive with a partner who can help in an emergency situation. A partner can help protect an unconscious diver experiencing a shallow water blackout from drowning and death. Before diving, the diver and partner should follow the proper SWB emergency procedure, which is to bring the partner to the surface as quickly as possible. Once on the surface, the partner would have to keep the unconscious diver’s head above the water to prevent him from drowning.
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