Which sign indicates that a lifeguard may need to provide first aid?

The presence of visible injuries like bleeding or swelling is a clear indication that a lifeguard may need to provide first aid. Such signs often imply that a person has sustained an injury that requires immediate attention, either to treat the injury itself or to prevent further complications. Recognizing these signs is crucial for a lifeguard, as responding quickly and appropriately to visible injuries can significantly impact the outcome for the affected individual.

In contrast, the other choices do not signify a need for first aid. For instance, patrons smiling or following all rules suggests that they are enjoying their experience and are safe, while the absence of visible injuries indicates that there are no current medical concerns needing immediate intervention. Recognizing when to step in and provide assistance is a fundamental skill for emergency responders, and being attentive to visible injuries is essential in ensuring the safety and well-being of patrons in the aquatic environment.