The duo got off to a great start to take the early lead at Lagoa Stadium, and after slipping to fourth place at the halfway mark, they fought back to grab second place in 7:02.51.
At one point lying more than six seconds behind New Zealand favourites Eric Murray and Hamish Bond, they crossed the line 2.80 seconds off the pace of the gold medallists.
The men’s pair bagged South Africa’s third medal of the Games, adding to silver medals secured by Cameron van der Burgh and Chad le Clos in the swimming pool earlier in the week.
“We’re pretty stoked. That was a quality race for us and we’re standing on the podium,” said Brittain, who survived a battle with cancer last year.
Earlier in the session on day six of the multi-sport Games, returning to the water after the regatta was delayed by poor weather conditions the day before, all four of the other SA rowing crews progressed to their respective A finals to be held on Friday.
The men’s (James Thompson and John Smith) and women’s (Ursula Grobler and Kirsten McCann) lightweight double sculls boats won their semifinals, while the men’s four (David Hunt, Jake Green, Jonty Smith and Vincent Breet) ended second in their race and the women’s pair (Kate Christowitz and Lee-Ann Persse) took third position in the penultimate round.
