Final answer:
A lifeguard should recognize and reach a drowning victim rapidly, and individuals who are unconscious in water may still have a chance of survival with prompt CPR. Drowning often occurs silently, so the lifeguard must be attentive to subtle signs of trouble. Bystanders should also take action to assist someone in need to overcome the bystander effect.
Step-by-step explanation:
A lifeguard on duty should have the ability to recognize a drowning victim promptly and reach them quickly. Despite common myths, a person who is unconscious in the water can often be saved, especially if they start receiving CPR within minutes and if their airway is sealed, preventing water from entering their lungs. Although it is commonly believed that drowning individuals will shout and wave for help, in reality, the muscular spasm that seals the airway prevents this, and their struggle may go unnoticed as the behavior can appear misleadingly calm.
Drowning can occur in surprisingly shallow depths, where even 30 mm of water can be fatal under certain conditions. In any emergency, including potential drownings, bystanders should be vigilant, observe their surroundings, and take action, combating the bystander effect by ensuring the person gets help or by notifying an authority figure.
In physics-related examples, such as calculating the height from which a rescuer in a helicopter drops a life preserver to a drowning person, knowns would include the initial velocity, the time taken for the preserver to hit the water, and the acceleration due to gravity.