(CNN)It was the first day of Jack Viglianco's summer job as a lifeguard. And his training was put to the test just 20 minutes in.
"I heard like a help, ah, kind of thing. And I looked over and I saw a guy who's probably like (3 feet, 6 inches), in the 4-foot water and gasping for air," 15-year-old Viglianco told CNN affiliate WJW.
The incident happened last week at the Charles A. Foster pool in Lakewood, Ohio.
A 4-year-old boy on a summer camp field trip was in the water, screaming for help.
Lakewood aquatics manager Matt Demaline said Viglianco had completed the five-hour orientation for new lifeguards a day earlier.
"We were ready to go, day one," Demaline said.
Viglianco told the affiliate that the rescue was one way to ensure he'll never forget this summer job.
"I was realizing that I just saved a kid's life," he said. "And that is something not many other people can say. Nothing my friends have ever said."