Police say the man and a woman were in a small boat on the eastern shore of Cold Lake on Monday night when both went overboard.
The woman was able to get back into the boat, but the man was not.
Sergeant Brent Sawatzky says the temperature of the water was around 4 Celsius when the man fell in.
Police were searching by air and using an underwater camera and sonar.
They are also trying to get divers from Saskatchewan to join the search.
The woman was treated in hospital.
Police don't know if alcohol was a factor.
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