What is shallow water blackout?

Shallow water blackout refers specifically to the loss of consciousness that occurs as a result of hypoxia, which is a deficiency in the amount of oxygen reaching the brain. This phenomenon typically happens in the water, especially during activities like prolonged underwater swimming or breath-holding. When a person holds their breath for an extended period, they may inadvertently lower the levels of carbon dioxide in their bloodstream, leading to a delay in the body's natural urge to breathe. As the oxygen levels drop dangerously low, the individual may lose consciousness without any prior warning.

Understanding this definition is crucial for lifeguards and anyone involved in water activities, as shallow water blackout can happen rapidly and without visible distress. This makes it imperative for lifeguards to monitor swimmers closely, especially during activities that may promote hyperventilation and prolonged breath-holding. The other options, while they describe different scenarios, do not accurately define shallow water blackout, which is specifically tied to the lack of oxygen—hypoxia—experienced underwater.