Stockwell won three medals at the 1984 Summer Olympics in Los Angeles. In the men's 100-metre freestyle, Stockwell finished in 50.24 seconds and claimed a silver medal behind American swimmer Rowdy Gaines's Olympic record time of 49.80 seconds. The outcome was controversial, however, because of a premature starter gun and a quick start by Gaines. Gaines's coach, Richard Quick, knew of starter Frank Silvestri's tendency to fire the starter gun almost immediately when the competitors mounted the blocks; as a result Gaines gained about a metre's head start on the competition, and held Stockwell off to claim the gold medal. Video of the event confirmed that Stockwell had not been set when the starter pulled the trigger. Stockwell and the Australian Olympic Federation lodged an official protest, but it was denied.