Final answer:
Depth markers should be provided on horizontal surfaces around the pool, on vertical surfaces within the pool, and at a minimum of every 20 feet to ensure safety for bathers and prevent diving into shallow water.
Step-by-step explanation:
To prevent a bather from diving into too shallow water, depth markers should be provided in multiple locations. They are necessary on horizontal surfaces around the pool where they can be easily seen by someone preparing to dive. They should also be placed on vertical surfaces within the pool for visibility when bathers are at water level. Additionally, to ensure safety, it is recommended that they be provided at intervals, such as a minimum of every 20 feet, to prevent areas of the pool from being mistakenly thought of as deep enough for diving. Hence, the appropriate answer to this question is D) All of the above.
It is crucial to highlight the reason why such precaution is important. Objects in water appear to be at a depth shallower than they actually are due to the refraction of light as it passes from water to air, which can mislead bathers about the actual depth. A misunderstanding about the depth of water can lead to severe injuries, as diving into shallow water increases the risk of injury to the nervous system. Understanding this optical phenomenon emphasizes the importance of clearly marking pool depths to prevent accidents.