Monk competed in his first
Commonwealth Games in 2006, after being asked to fill in for
Ian Thorpe. He finished seventh in the 100m freestyle event, and ninth in the 200m. As a member of the Australian men's relay team, he won gold in the 4×100-metre medley (as a heat swimmer) and bronze in the 4×200-metre freestyle. Later that year he competed in the
2006 Pan Pacific Swimming Championships, finishing sixth in the 200-metre freestyle, and taking the bronze medal in the men's 4×100-metre and 4×200-metre freestyle relay events. an achievement that he regarded as one of his best. In 2008, Monk won two gold medals at the
FINA Short Course World Championships in the 200m freestyle individual competition and the men's 4×200-metre freestyle relay. Subsequently he finished third in the 4×200-metre freestyle relay at the
2009 World Aquatics Championship and fifth in the individual 200-metre freestyle. His second
Commonwealth Games was the following year, in 2010, where Monk won silver in the individual 200 m freestyle and gold in the 4×200-metre freestyle relay. In 2012, in the 200-metre freestyle, Monk finished 2nd behind
Thomas Fraser-Holmes at the Australian trials in
Adelaide and qualified for the London Olympics. In London, he finished 13th in the individual 200-metre freestyle and 5th in the 4×200-metre freestyle relay. ==Accident and police investigation==