RCMP say Kevin Boutilier was in a rented houseboat with several friends when someone's hat blew into the water in the Narrows area of the lake.
It appears Boutilier and several others jumped into the water to retrieve the hat, but the houseboat began drifting away because of rough water conditions.
Two of the individuals in the water appeared to be in distress, so several others dived in to assist.
RCMP say Boutilier was last seen in distress and going under the surface several times. He did not resurface in spite of a friend's efforts to aid him.
All others made it safely back to the boat.
At the time, Boutilier was wearing a pair of red shorts.
Rescue teams worked with police to search the area, including nearby shorelines but found no trace of him.
RCMP say crews are considering several options for his recovery, but this area of the lake is very deep and the terrain on the bottom of the lake presents challenges for divers as well as the use of sonar equipment.