At the age of 14, David Smith was competing in surf lifesaving, iron man and kayak. In 2003 he was named Outstanding Junior Paddler at the Australian Championships, winning four gold medals. At 21, he was selected in the Beijing Olympic Team after he won the K4 1000m and K2 1000m (with Ken Wallace) at the 2008 National Championships. He went on to finish tenth in the K4 1000m event in Beijing.
Looking for a better performance at the London Games, Smith again qualified in the K4 1000m event as well as the K2 1000m event. Lining up alongside Murray Stewart, Jacob Clear and Tate Smith in the K4, the Australian crew won their semi-final to ensure they would better the result Smith had at the 2008 Games. The crew was not content with simply making the final though. They led at each mark to win the gold medal ahead of Hungary and the Czech Republic.
The win came a day after Smith in agonising 4th place in the K2 1000m event with Beijing gold medallist Ken Wallace.