What is one consequence of shallow water blackout?

The correct response focuses on the immediate need for rescuer assistance as a consequence of shallow water blackout. Shallow water blackout occurs when a diver hyperventilates before diving, lowering carbon dioxide levels and masking the sensation of breathlessness. This can lead to a sudden loss of consciousness underwater, making the diver unable to respond or swim back to the surface. As a result, such an incident necessitates immediate intervention by a rescuer who must quickly locate and safely bring the unconscious diver back to the surface, as any delay could be life-threatening.

The other options, while they may relate to the dive experience, do not directly capture the critical and immediate life-threatening nature of a shallow water blackout. For example, while an increase in swimming speed or an emotional response like panic could be associated with struggle or distress underwater, they do not reflect the situation's dire need for rescue or assistance that directly follows a blackout. An accidental descent underwater can happen due to various factors, but it is not a direct consequence of the blackout itself; rather, it describes what might happen afterward.