Loss of consciousness most often occurs during which stage of cold water immersion?

Loss of consciousness due to cold water immersion most commonly occurs during the stage known as longer-term immersion, which is associated with immersion hypothermia. As an individual remains in cold water for an extended period, the body loses heat rapidly, which can lead to a significant drop in core body temperature. This condition can impair brain function and result in confusion, disorientation, and ultimately unconsciousness.

In contrast, during the initial immersion phase, the body experiences cold shock, which can cause an immediate gasp reflex and hyperventilation, but this is typically not accompanied by loss of consciousness. Short-term immersion may lead to various physiological responses as well, but it is not usually associated with hypothermia severe enough to cause unconsciousness. Rewarming shock, while it can be dangerous and lead to shock or other complications, occurs after exiting the cold water and is not a stage of immersion itself. Therefore, immersion hypothermia, associated with prolonged exposure to cold water, best explains why lost consciousness is most likely to occur during this stage.