Search crews are scouring a northeast Tennessee lake for the body of a Kentucky man who apparently drowned.

The man was out with his family Sunday when he fell off a boat and into the water.

His name has not yet been released at this time.

The incident happened at Norris Lake in Claiborne County, Tennessee.

"They said he was a very good swimmer, but he did not have a life jacket on," said Bruce Myers, Claiborne County, Tennessee Rescue Squad. "They thought they'd ran out of fuel, the guy leaned over to check the fuel tank, and rolled in and didn't come back up."

Search crews say the heat is also making their jobs harder.

They say they're having to stop frequently for water breaks.