What should determine the size and location of a zone?

The size and location of a zone are primarily determined by the ability to see every area of that zone to ensure effective surveillance of all swimmers within it. A lifeguard must be able to monitor all activities and immediately identify any potential emergencies. This visual coverage is critical for ensuring the safety of swimmers, as it allows the lifeguard to quickly respond to situations, such as distress or accidents.

While other factors do play a role in establishing a zone, such as depth of water, the number of swimmers present, and the availability of rescue equipment, they do not directly impact the lifeguard’s ability to visually oversee the area. Depth can influence the type of supervision needed but does not determine the visual coverage necessary. Similarly, while knowing the number of swimmers can affect the lifeguard's workload and potential risks, it is still the ability to see everyone that remains the priority. Lastly, availability of rescue equipment is crucial for response but does not influence the size or placement of a zone in terms of visibility.