Max, wearing a GoPro camera, dove into the water and discovered an upturned car about 15 feet below the surface, just 10 feet from the TransCanada Highway.
Investigators later determined the 1986 black Honda Accord was owned by Janet Farris, 69, who had been driving alone to a wedding in Alberta when she went missing in 1992, CBC reported.
Good memories of his mother helped her son, George Farris, deal with the loss.
"After the first year, you just carry on," Farris, 62, told CTV. "You come to live with it."
He is thankful to have closure.
"I think the worst thing was not knowing," Farris told CBC. "We kind of assumed that maybe she had gone off the road or fallen asleep or tried to avoid an accident or animal on the road."
Investigators are praising Max for his sleuthing skills.
"The RCMP will probably be looking at this guy down the road for potential employment," Cpl. Thomas Blakney told CTV with a grin.