USA’s relay won the 400 medley relay with a world record of 3:29.34, beating their own world record of 3:30.68 set at the Olympics in Athens 2004, and securing Phelps his record breaking 8th gold medal. The Australian women also set at 400 medley relay world record, beating their own world mark of 3:55.74 with a new world record of 3:52.69.