Which of the following actions can worsen the effects of cold water immersion?

Drinking alcohol prior to immersion can significantly worsen the effects of cold water immersion for several reasons. Alcohol has a vasodilating effect, meaning it causes blood vessels to dilate and increases blood flow to the skin. This can lead to a false sense of warmth, as the individual may feel warmer initially. However, this increased blood flow to the skin can accelerate heat loss from the body, making one more susceptible to hypothermia in cold water conditions.

Additionally, alcohol impairs judgment and coordination, which can hinder one's ability to react appropriately in a cold water situation. For instance, individuals under the influence of alcohol may be less likely to recognize the severity of their situation, and they might also struggle with physical tasks such as swimming to safety or keeping themselves afloat.

In contrast, wearing insulated clothing can help retain body heat, swimming vigorously could provide some warmth through increased physical activity (though it can also lead to exhaustion), and staying calm and still is often recommended to manage energy expenditure and reduce heat loss. All these alternative actions either promote safety or help maintain body temperature in cold water.