Synchronised swimming was an event which was not initially oversubscribed.
When sessions for the sport were put back up for sale, a human data error meant thousands of extra tickets, which did not exist, were made available.
A total of 3,000 customers who bought tickets in the second round of sales have been contacted by Games organisers Locog.
They have been offered the chance to exchange their tickets for other events for which they also applied, and were originally unsuccessful.
Many of those with synchronised swimming tickets could actually end up swapping them for some of the highest profile events at the Olympics, like athletics and diving.
London 2012 - Begin your journey here
"In December we contacted around 3,000 customers who had applied for tickets in the four sessions during the second round sales process. We are exchanging their synchronised swimming tickets for tickets in other sports that they originally applied for."
Ticketing has been one of the toughest challenges for London 2012.
Hundreds of thousands of applicants failed to obtain any tickets, and there were complaints last summer when the official website struggled to cope with the huge demand.
More than a million extra tickets are due to go on sale in May.
These had been held back by Locog while seating positions were confirmed at al the venues. It is some of these tickets which have now been made available to those who had originally been expecting to watch synchronised swimming.