Mercer grew up in Thirroul on the NSW south coast and competed professionally for nearly three decades.
Throughout his illustrious career, he won five state NSW championships, two Test of the Toughest titles, the 1997 World Oceanman series and two Australian Ironman titles.
Mercer retired in 2010 and was inducted into the NSW Hall of Champions in 2014 alongside the likes of Dawn Fraser and Don Bradman.
Our thoughts are with his family.
This article originally appeared on New Idea