What item is commonly used by lifeguards to signal an emergency?

The whistle is a universally recognized signaling tool employed by lifeguards to indicate an emergency. It serves multiple functions, such as gaining attention, alerting swimmers to potential hazards, and coordinating rescue efforts. The sharp, piercing sound of a whistle can effectively cut through environmental noise, making it an ideal choice for communicating in loud beach settings.

While other items like a flashlight might be useful in low-light situations or for signaling at night, a whistle is predominantly the first line of communication during emergencies, especially during daylight and in busy beach environments. Radar devices and hand mirrors do not serve the same immediate and effective signaling purpose in emergencies as a whistle does. Thus, the whistle remains the primary tool for lifeguards to efficiently manage safety and communicate alerts to the public.