Which of the following accurately describes shallow water blackout?

Shallow water blackout is specifically characterized by a loss of consciousness that occurs due to hypoxia, which is a deficiency of oxygen reaching the tissues. This phenomenon typically happens in situations where a diver hyperventilates before diving. Hyperventilation reduces carbon dioxide levels, which can delay the urge to breathe. As the diver ascends, the oxygen levels drop due to exertion or inadequate air supply, leading to unconsciousness at shallow depths before the diver realizes they are in trouble.

This condition is particularly dangerous because it can happen suddenly and without warning, especially when a diver is operating in shallow waters, where the misconception is that there is enough time to react. The other options do not accurately describe the cause or nature of shallow water blackout. Nitrogen narcosis pertains to deeper dives and does not relate to oxygen deprivation. Excessive carbon dioxide retention represents a different set of physiological responses and risks. Rapid ascent primarily refers to potential injuries such as decompression sickness or barotrauma, which are not connected to the loss of consciousness seen in shallow water blackout.