Which of the following is a sign that a swimmer may be in distress?

A sign that a swimmer may be in distress is excessive splashing and difficulty staying afloat. This behavior indicates that the swimmer is struggling to maintain their position in the water, which can be a clear indicator that they are overwhelmed or in need of assistance. Signs of distress often manifest through physical struggle, as the swimmer attempts to keep their head above water or fight against waves, leading to increased splashing.

In contrast, swimming calmly with confidence suggests that the swimmer is secure and capable in the water, indicating no distress. Waving and shouting for help, while an indication of a need for assistance, may not always reflect a struggle in the water itself. Lastly, swimming towards the shore typically demonstrates a swimmer's ability to navigate effectively and is often associated with a sense of stability rather than distress. Thus, the behavior characterized by excessive splashing and difficulty staying afloat is the most definitive sign of a swimmer in distress.