RCMP say the 35-year-old man was rafting with four friends on the Highwood River on Sunday afternoon when their raft went over a waterfall and flipped.
The others made it to safety, but the man who died drifted downstream where swimmers saw him floating face down.
Police say they pulled him from the water but had to scramble up a steep 60-metre bank to call for help.
They say the victim was wearing a helmet and a life jacket.
Police say he was from Calgary.