This is Cameron van der Burgh.
In the breaststroke, swimmers are allowed a single dolphin kick (which is exactly what it sounds like) when they enter the pool, and one after each turn.
With no official underwater video judging at the Olympics, swimmers sometimes try to sneak extra kicks. This video shows van der Burgh employing three dolphin kicks in his gold-medal and world-record-setting run.
One would expect the gold medalist to stay quiet on the issue, but when asked about it by the Sydney Morning Herald, he readily admitted to breaking the rules.
According to NBC, the IOC and FINA (the international governing body of swimming, diving, water polo, etc.) are not expected to rule against the South African swimmer.