At the 2012 U.S. Olympic Trials in Omaha, Nebraska, the qualifying event for the U.S. Olympic team, Shanteau made the U.S. Olympic team by finishing second in the 100-meter breaststroke. At the 2012 Summer Olympics in London, he placed fourth in the second semi-final of the 100-meter breaststroke and did not advance to the final. He earned a gold medal by swimming the breaststroke leg for the winning U.S. team in the preliminaries of the 4×100-meter medley relay.