A male dove from a boat on Ness Lake Thursday to get his young son who was swimming with a floatation device and had drifted a short distance away.
With a friend's help the two were able to get the child back in the boat.
The father, who was not wearing a flotation device, went under the water and did not surface again.
Witnesses on scene helped look for the man but were unsuccessful.
Search and Rescue performed a limited depth, underwater search but could not find the man.
The RCMP Underwater Recovery Unit will attend to perform a deeper more extensive search.
Names are withheld pending notification of next of kin.
