(CBS-DETROIT) – A 84-year-old Michigan man drowned in Oakland County over the weekend, marking the county’s eleventh drowning of 2024.

According to the Oakland County Sheriff’s Office, Louis William Petro of Sylvan Lake was found at 10 p.m. Friday after his unattended boat was found drifting hours earlier.

Divers from the Oakland County Sheriff’s Search and Rescue Team and the Southeast Michigan Dive Group found Petro in five feet of water, about 200 feet from shore. Officials said Petro was not wearing a life jacket.

The preliminary cause of death was drowning, but the sheriff’s office investigation is ongoing.

Other boaters had seen Petro, a regular boater on the lake, launch his 18-foot Glastron boat onto the lake at 2:30 p.m. Friday. He was alone on the boat.

Then, at 5:15 p.m., his boat was seen unattended. After the drifting boat was reported to authorities, other boaters tied Petro’s boat down so it would not interfere with other boaters.

Authorities found Petro’s cellphone, wallet and car keys on the boat. There were no signs of a struggle or infidelity, nor any signs of alcohol or drug use.

Chesterfield Township Public Safety Divers and the Macomb County, Lapeer County, Livingston County, Genesee County and Wayne County Sheriff’s Offices assisted in the investigation.

Drone and flight units as well as boats equipped with side-scan sonar technology also assisted.

“In what has already been an extremely tragic summer, the loss of another person enjoying the water is very sad,” said Oakland County Sheriff Michael Bouchard. “While we do not yet know what happened in this case, we encourage people who are not strong swimmers or are alone in the water to consider using a flotation device.”

In the last month alone, there have been several drowning accidents in Oakland County, including the following: