Which of the following is a sign of heat-related illnesses in water?

The presence of a rapid pulse and confusion are significant indicators of heat-related illnesses, such as heat exhaustion or heat stroke. In the context of heat-related illnesses experienced in a water environment, these symptoms indicate that the body is struggling to maintain a safe internal temperature.

A rapid pulse suggests that the body is attempting to cool itself down by increasing blood flow to the skin and precipitating sweating. Confusion is a critical symptom that can indicate a more severe state, such as heat stroke, where the body's temperature regulation fails and mental functioning is compromised. Recognizing these symptoms is crucial for lifeguards and those supervising water activities, as timely intervention can help prevent serious complications associated with prolonged exposure to high heat stress.

The other options, such as excessive shivering and cold skin, are more closely associated with cold-related illnesses rather than heat-related conditions. Bright red skin may certainly appear in cases of heat exposure, but the combination of rapid pulse and confusion is a more direct indication that immediate action is necessary.