In what case is it necessary for a lifeguard to use a whistle?

Using a whistle is essential for gaining the attention of patrons in case of an emergency, as it serves as a loud and effective way to alert individuals to immediate situations that require their prompt response. Whistles can penetrate background noise better than a lifeguard's voice and can carry over distances, making them an invaluable tool during emergencies such as a sudden water rescue or a medical situation. Their distinct sound helps to immediately signal urgency and directs patrons to react promptly, ensuring safety and quick response to the situation at hand. This makes it crucial for lifeguards to utilize a whistle effectively to manage emergencies and maintain the safety of all swimmers.