Which of the following would be considered a potential hazard during a water rescue?

Fast-moving currents and debris present significant dangers during a water rescue. Such conditions can drastically affect the stability and safety of both the rescuer and the rescued individual. Debris can cause injury or entanglement, making it difficult for rescuers to reach victims or for victims to stay afloat. Additionally, fast-moving water can increase the risk of being swept away, making it harder to maintain control of the rescue effort. Understanding these hazards is crucial for effective water rescue planning and execution, as they directly impact safety protocols and methods employed in a rescue scenario.

The other options, while relevant to a rescue operation, do not introduce the same level of immediate peril as fast-moving currents and debris do. Calm weather conditions, wide open spaces, and the presence of lifeguards can actually contribute positively to the safety and effectiveness of a rescue effort.