Final answer:
The size of the zone should allow for a lifeguard to recognize an emergency, reach the victim, extricate, and provide ventilations within minutes. This is because brain cells start to die after about six minutes without oxygen.
Step-by-step explanation:
The size of the zone should allow for a lifeguard to recognize an emergency, reach the victim, extricate and provide ventilations within minutes. The reason for this is that the longer the brain goes without oxygen, the more likely brain cells will die. Brain death is likely after about six minutes without oxygen. Therefore, a lifeguard needs to be able to respond quickly within a few minutes to provide the necessary help to save a drowning victim.