Actually, the answer may be quite simple: It's called, "perceptual blindness," and to save more lives, it's imperative that the industry understand it.
In this way, perceptual blindness can help explain why lifeguards fail to detect victims on the bottom of swimming facilities.
Although a lack of vigilance often produces poor surveillance on the part of lifeguards, it appears that even the most vigilant observers suffer from perceptual blindness. In fact, the more vigilant one becomes in preventing accidents, the more prone one may be to missing a body on the bottom of the pool.
To date, there is no "cure" for perceptual blindness, but knowing that it exists may help lifeguards be more attentive to the bottom.
The first step in dealing with perceptual blindness is to understand it more and acknowledge that it does exist.