What maneuver is described as an alert for an active rescuer to come in for assistance?

The correct answer is that the maneuver described as an alert for an active rescuer to come in for assistance is the "three whistle blasts." This signaling technique serves as a clear and audible alert for lifeguards on duty. When three whistle blasts are heard, it indicates that immediate attention is needed due to a potential emergency or a situation requiring back-up.

This signaling method is critical in a busy beach environment where verbal communication may be difficult due to noise from waves, crowds, and other distractions. The unmistakable sound of three distinct whistle blasts catches the attention of fellow lifeguards and prompts them to respond quickly, ensuring that the rescuer in need can get the support necessary to manage the situation safely.

The other options outlined do not serve the same purpose or lack the specific recognition needed in emergencies. The "ready position" refers to the stance a lifeguard takes before entering the water, while "eye contact" is an important communication method but does not serve as a formal alert system. The "rescue flag protocol," while crucial for signaling the conditions or potential dangers in the water, does not specifically indicate that a rescuer requires immediate assistance.