On Thursday, Outlook RCMP received a complaint at 6:40 p.m. regarding a possible drowning.
According to police, a man and woman were swimming in the lake when the man disappeared.
The woman made it to shore but could not find the 35-year-old man in the lake or onshore.
As of Friday, he remains missing. He was last seen in the area of Danielson Provincial Park.
Outlook RCMP, the Outlook Fire Department, the Ministry of Environment and the Civil Air Search and Rescue Association have mobilized for the search.
Members of the public are also searching the lake and shoreline by boat, ground and air.