A 59-year-old man, after fishing with his father, jumped into the Tennessee River about a mile south of the state Highway 60 bridge Thursday and wasn't seen again.
The man's father jumped in after him, Tennessee Wildlife Resources Agency spokesman Dan Hicks said, but the father started struggling until two witnesses came over and saved him.
The father and son were fishing when the son said he was hot and began swimming to cool himself at 2:30 p.m.
Hicks said names of the father and son won't be released until family members have been notified.
The boat was in about 40 feet of water when the men went over the side, officials said.
Hamilton County, Rhea County, Dallas Bay and state officials searched for the Sale Creek man's body until 10 p.m. Thursday and planned to resume the search at 8 a.m. today.
Hicks said there's no way to know how long the search may take, but the river's current means the search today will cover an even larger area.