Port Alberni RCMP say they launched their police boat around 4:30 p.m. PT Saturday in response to reports of an on-the-water incident on Sproat Lake in the Alberni Valley.
Quick-acting bystanders were able to rescue one man from the lake. He was later airlifted to hospital in Victoria.
By the time emergency crews arrived, police say the boat was fully submerged.
The second, 41-year-old man was aboard at the time of the accident, police said.
The RCMP's Underwater Recovery Team found the body on Sunday. The wreckage of the boat was also recovered.
Police say they don't yet know how or why the boat sank but that an investigation is underway.
The man's name has not been released.
Google Map: Sproat Lake