Sullivan became the fastest swimmer in history after he broke the world 50 m freestyle record at the 2008 NSW Open Championships at Sydney International Aquatic Centre. He timed 21.56 to slash 0.08 off the 21.64 set by the Russian Alexander Popov at Moscow in June 2000. However his time was beaten to 21.50 by French Alain Bernard on 23 March 2008. He significantly improved his last PB standing at 22.00 s. He declared he had had positive feelings of being in a good form for the race earlier on. Shortly after, he swam for West Coast club in the 4 × 100 m freestyle Relay and clocked 48.11 s, cutting 0.07 off Michael Klim record set for Australian relay at the 2000 Olympics. His time was also a Commonwealth record, knocking 0.06 s off the previous time gained by South African Roland Schoeman.
