When the man went under the water, Lara McKenzie first thought he was playing with his daughter. He wasn't panicked, flailing his arms or yelling.

When the man went under the water, Lara McKenzie first thought he was playing with his daughter. He wasn't panicked, flailing his arms or yelling. He was simply there, and then he wasn't. A moment passed, and when the man didn't pop up elsewhere, McKenzie knew it wasn't a game of hide-and-seek in the pool. She and another lifeguard made eye contact, yelled for someone to call 911, jumped in and saved his life.

"He wasn't even sure what had happened," McKenzie recalled recently. "He came back and talked to us a couple days later. His doctors thought he may have had a stroke or something."

Though everything turned out OK, the moment seared itself into the then-teenager's mind and taught her a valuable lesson. Drowning can happen to anyone, adults included, but also children who know how to swim. And it can happen quickly and silently.

Today, McKenzie is the principal investigator for the Center for Injury Research and Policy in the Research Institute at Nationwide Children's Hospital, where she focuses on reducing injury-related pediatric death and disability. Part of that work includes drowning prevention.

Drowning is the leading cause of unintentional death in children between the ages of 1 and 4. Even more alarming, perhaps, is the fact that every five days in the summer, a child in this country drowns in a portable pool.

"We think of those little kids and those inflatable pools as a safe alternative, but really they can drown in as little as an inch of water," McKenzie said. "Anything that has water-buckets, bathtubs, toilets, sinks, portable pools, pools, hot tubs-anything that can collect water essentially."

One of her main messages to parents when it comes to water safety is to be vigilant. Don't be distracted by cellphones, books or conversation. It only takes a few seconds for tragedy to strike.

Perhaps the biggest step parents can take to ensure their kids are safer around water is to enroll them in swim lessons, if they haven't had them already.

At the Downtown YMCA in Columbus, swim lessons start at 3 years old, though swim and lifeguard instructor Sarah Huggins said lessons should start as early as possible.

"It gets rid of the fear that can be associated with water, and at the same time it increases the safety and respect for the water that kids need to have," Huggins said.

Swim lessons shouldn't be a seasonal activity, said Lisa Armitage, owner of Goldfish Swim School. Learning to swim should occur year-round, because kids can forget a lot of what they learn by next summer.

"When there is a perpetual lesson, similar to music lessons, children are constantly learning and building on the skills they've acquired," Armitage said. "That allows children to progress at a much more rapid pace."

When children are in the pool-even if they're experienced swimmers-it's important to watch for fatigue. That's one of the main reasons public pools enforce mandatory breaks every hour.

Lesser-known threats such as dry drowning and secondary drowning stem from breathing water in, often due to fatigue or roughhousing, McKenzie said.

"Most of the kids who have any kind of close call in the water do fine, but about 5 percent don't, and those few can go on to develop dry drowning or secondary drowning," McKenzie said.

Dry drowning gets its name because it occurs out of the water, potentially hours after a child has left the pool. The same goes for secondary drowning. In dry drowning, a child breathes in water, which causes vocal cord spasms that close off airways. With secondary drowning, water gets into the lungs and interferes with breathing.

The symptoms to look for in both cases include shortness of breath, difficulty breathing, coughing or chest discomfort, fatigue, irritability and behavioral changes. If a child experiences any of those symptoms, McKenzie said, call 911 immediately.

"Don't wait and watch," she said.