Ronald Carty was reported missing around 7:30 p.m. at the Norton Reservoir after he dove into the water and did not resurface, the Bristol County District Attorney's Office said.
He'd been boating with two other men for about an hour when he jumped into the water. They attempted to rescue him but couldn't, the DA's office said.
First responders pulled him from the water around 11 p.m., officials said.
Investigators do not believe there was any foul play in Carty's death.
Click here to follow Daily Voice Dorchester and receive free news updates.