What is the most appropriate action to take when providing care to a swimmer who is developing shock?

The most appropriate action when providing care to a swimmer who is developing shock is to cover the swimmer with a blanket to prevent heat loss. This is crucial because one of the primary responses to shock is a drop in blood pressure and potential body temperature regulation issues. Covering the swimmer helps to maintain body warmth, which can be essential for stabilizing their condition. Hypothermia can exacerbate the symptoms of shock, so keeping the swimmer warm is a vital step until professional medical help arrives.

The other actions listed may not be suitable in this scenario. Administering cold water could lead to further complications, as it risks lowering the body temperature in someone already potentially experiencing shock. Having the swimmer lay flat on their back can sometimes be appropriate, but it's generally better to ensure they are in a position that promotes breathing and comfort. Providing sugary drinks immediately may not be safe as well, since administering anything orally when someone is unwell—especially with symptoms of shock—can be risky, particularly if the swimmer is feeling faint or might need further medical intervention.