Authorities identified the man as David Hart. Hart's body was recovered at approximately 8:30 p.m., about two hours after he went under.
Deputy Keshia Guyll, spokeswoman for the Benton County Sheriff's Office, said the man was in the area restricted for swimming when he went under in about 12 feet of water. The incident happened shortly before 6:30 p.m. near the Rocky Branch Marina.
Guyll said alcohol was not a factor.
"It's terrible," Guyll said. "We want people to come out and have a good time in our lakes, and when something like this happens, it's a terrible, terrible situation."
Hart's body was taken to the coroner's office.
Hart is a former Har-Ber High School student.