Canada ended up 1-2 in Pool C play on Friday, surrounding the win over South Africa with losses to Wales and Samoa.
Canada opened play with a 26-17 loss to Wales. Nathan Hirayama, John Moonlight and Tyler Ardron all scored tries for Canada, but Wales got past the goal-line four times to overcome Canada's offence.
Canada rebounded with the upset over South Africa. Sean Duke scored a quick try to give Canada a 7-0 advantage just seconds into the match.
Hirayama later converted his own try, and Canada led 14-10 at the half.
Duke scored his second try of the match early in the second half, then Moonlight put the game away for Canada as he bowled over the goal-line.
South Africa scored three tries in the match, but gave up valuable points when they were unable to convert any of them.
Canada couldn't keep the momentum going against Samoa, falling 26-12.
Lio Lolo broke open a 7-7 tie with a pair of tries, and Canada was unable to recover.
Philip Mack and Duke scored tries for Canada.
With three tries, Duke is tied for third in the tournament. Hirayama is tied for second in scoring with 20 points.
Canada takes on Tonga on Saturday in the Bowl quarter-final. The loser gets relegated to the Shield competition.