lifeguards. The startling story all parents need to see on this holiday weekend, when so many of us are heading to the pools and the beaches. It turns out your children may not be safe, even if... See More
lifeguards. The startling story all parents need to see on this holiday weekend, when so many of us are heading to the pools and the beaches. It turns out your children may not be safe, even if there's a lifeguard on duty. Reena ninan has that story. Reporter: Good morning, Amy. You expect the lifeguards to protect you and your children from the perils at the pool. But we found out, that isn't always the case. Lifeguards. Buff and brave. Ready to jump in at the first sign of danger. Right? Well, maybe not always. Meet 23-year-old Harris, a former lifeguard at several pools in Texas. He's blowing the whistle on what he says are shocking secrets of life on the lifeguard tower. A lot of lifeguards are not prepared for something bad happening. Reporter: Roughly 4,000 Americans drown each year. And one in five children that brown in swimming pools, do so with a lifeguard present. There are examples of lifeguards behaving badly. Look at this lifeguard, tuning out the pool and listening to his iPod. No lifeguard should be given electronic equipment. No texting or talking on the phone. Reporter: Worst is this guard. He's gone into hibernation mode. No one is swimming. And it's challenging to spot a kid drowning, as I found out myself, with a test dummy, named Timmy. How hard can this be? Timmy is at the edge of the pool. A spot where wall huggers drown. I never saw it. Never once. We put these young lifeguards to the test with our mannequin, Timmy. Remember 18-year-old Blake has no idea this is a drill. In less than five seconds, Blake sees something. And explodes into action. Did you think it was a real kid drowning? I'm just scanning the waters, and I see something out of the norm, I go check it out. Doesn't make a difference to me. Reporter: What should you look out for? And how many lifeguards are on duty? And who is paying attention? Check out clear the water is. Dirty or cloudy. It's impossible to spot a swimmer in those types of circumstances. And experts remind us, don't be afraid to confront management. It's so uncomfortable to do that. But it's better than dealing with a trip to the E.R. Or even worse. One of five kids who drown with a lifeguard present. Unbelievable stats. Thank you, Reena. You can see more of Reena's report and so much more on "20/20" at 10:00 eastern, right here on ABC.
This transcript has been automatically generated and may not be 100% accurate.