Olympic rules allow one dolphin kick at the start of a 100-meter breaststroke race.
In a dolphin kick, the swimmer's body moves like a wave in the water, resembling the movement of a dolphin. The intensity of the wave created propels the swimmers forward faster underwater than if they were on the surface of the water.
Underwater footage of van der Burgh's start revealed him doing more than the one — some reports said he did three — dolphin kicks. He won in a world record of 48.46 seconds.
Van der Burgh admitted he did the extra kicks but said he was forced to because the rule was not policed properly and illegal kicking had become common.
As the fastest qualifier for the Olympic final, van der Burgh swam in lane four, which is lined with numerous television and still cameras that clearly documented the infraction. But the cameras are for TV use only, and the judges cannot look at the images.
"Judges can only judge what they see," Cornel Marculescu, the executive director of swimming governing body FINA, told The Associated Press on Wednesday. "They cannot judge what they don't see."
Illegal dolphin kicks are common in breaststroke events. At the 2004 Athens Games, American backstroker Aaron Peirsol accused Japanese winner Kosuke Kitajima of using a dolphin kick at the start of his race after watching teammate and world record-holder Brendan Hansen finish second.
This time, Hansen took bronze behind Van der Burgh and Christian Sprenger of Australia.
"If you're not doing it, you're falling behind," van der Burgh told the Sydney Morning Herald. "It's not obviously — shall we say — the moral thing to do, but I'm not willing to sacrifice my personal performance and four years of hard work for someone that is willing to do it and get away with it."
FINA wanted to install underwater video use at its last two world championships in Rome (2009) and Shanghai (2011), but host broadcasters protested because of the cost. It would require three cameras in each of the eight lanes.
But after a new controversy it may not be an option anymore. FINA discussed the possibilities of underwater video with coaches at a meeting Sunday to wrap up the pool competition.
"This is something to be looked at by the technical swimming committee," Marculescu said, adding that a decision on video use could come at the next FINA congress at the 2013 world championships in Barcelona.
In the meantime, the South African Sports Confederation and Olympic Committee on Tuesday issued a statement "surrounding the media interest" in van der Burgh's admission.
South Africa delegation leader Patience Shikwambana said she had spoken with the manager of the aquatic squad, Shaun Adriaanse, who is also Swimming SA's chief executive officer.
"It's clear and simple," Shikwambana said. "There is really no point in commenting on media reports. Suffice to say we haven't been informed by FINA of anything untoward and neither have we heard anything from the International Olympic Committee."
Meanwhile, there is also discussion in swimming circles of eliminating the women's 800-meter freestyle race and replacing it with a 1,500 free — the longest race in the pool. That would make the men's and women's programs the same.
At world championships, both men and women race the 800 and 1,500, and women have shown how far they can swim by competing in marathon races like the 10-kilometre event, which was introduced to the Olympic program four years ago.
"The women can do the 1,500," Marculescu said. "Why not?"
American 15-year-old Katie Ledecky won the 800 free in London ahead of Spain's Mireia Belmonte Garcia and defending champion Rebecca Adlington of Britain.
AP Sports Writer Gerald Imray contributed to this report.