He sustained “life-threatening injuries” and died about an hour-and-a-half later, police said, adding that a report would be prepared for the coroner.
A Queensland ambulance spokeswoman told AFP on Sunday that he died at the scene after sustaining a “significant life-threatening wound to his neck”.
Humpy Island, which lies in the Great Barrier Reef’s Keppel Bay Islands National Park, has a popular camping ground that gives easy access to reefs for diving and snorkeling.
Community leaders spoke of their distress at the loss of Luke Walford, a youth pastor at the Cathedral of Praise church in the central Queensland town of Rockhampton.
Walford, who had posted photos on social media of himself in a wetsuit during a previous fishing trip, was believed to have been spearfishing at the time of the attack.
“We are all very much still in shock,” said Donna Kirkland, who represents Rockhampton in the Queensland state parliament.
“A family friend, not only to my own family but countless others. He was an inspirational leader as a children’s and youth pastor,” she said in a statement.
“My prayers and heartfelt condolences are with his beautiful family and indeed the many who will be devastated, as I am, at this news.”
The pastor of Cathedral of Praise, Claude Fingleton, said Walford was “greatly loved”.
“This was a young man who loved people, who loved God,” he told national broadcaster ABC.
The country’s last fatal shark attack was in December 2023, when what was believed to be a great white killed a 15-year-old boy at a remote surfing spot in South Australia.
There have been more than 1200 shark incidents in Australia since 1791, of which over 250 resulted in death, according to a national database.
Four others have been attacked by sharks in Queensland in 2024, according to an incident tracker.
