The man was attacked at around 2 p.m. near Indian Head on the eastern side of Fraser Island. A doctor and nurse at the scene provided first aid until paramedics arrived and were winched down by helicopter. They provided emergency treatment but the man, who had been bitten around the legs, could not be saved and died at the scene, said the Queensland Ambulance Service.
The attack happened not far from where 23-year-old Queensland wildlife ranger Zachary Robba was fatally mauled by a great white shark in April.
Queensland police were not immediately able to identify the victim in Saturday's attack. They said a report was being prepared for the coroner.
“Our deepest condolences go to this young man’s family and friends,” he said. “The loss of a young life with his future before him is a tragedy beyond words. We share their sadness and grief.”