Which of the following is a common sign of someone in distress in the water?

The presence of flailing arms indicates a person in distress in the water because it typically signifies panic or a struggle to stay afloat. When individuals are in trouble, their natural instinct may be to wave their arms in an effort to attract attention or to try to keep their heads above water. This chaotic movement is markedly different from intentional or controlled swimming strokes, which would suggest a swimmer is competent and untroubled.

In contrast, calm floating on their back would imply that a person is relaxed and in control of their situation, rather than experiencing distress. Similarly, peaceful swimming strokes indicate that a swimmer is experienced and not in need of assistance. Lastly, reading a book on the shore clearly reflects a situation where a person is not in the water at all, thus posing no risk or distress. Recognizing these signs is essential for effective swift water rescue operations, as they help responders identify who might need urgent help.