Which factors can affect the water conditions at a pool or beach?

Water conditions at a pool or beach are directly influenced by various environmental and natural factors, making the selection of weather, temperature, wave action, and water clarity the most relevant choice.

Weather conditions, such as rain or storms, can lead to changes in water quality, potentially introducing contaminants or altering temperature. Temperature plays a crucial role in the comfort of the swimmers and can affect water clarity and algae growth. Wave action is particularly significant at beaches, where stronger waves can churn up sediments and impact visibility and safety. Water clarity is essential not only for aesthetic purposes but also for safety, as it affects a lifeguard's ability to see swimmers in distress.

In contrast, options that reference maintenance costs, staffing levels, visitor numbers, or cleanliness focus more on operational aspects rather than the physical conditions of the water itself. While these factors are important for the overall management of a facility, they do not directly impact the water quality or conditions as the aspects mentioned in the correct choice do.