The 17-year-old was bitten on the upper thigh at Rudder Reef off Port Douglas, about 60 kilometres (37 miles) north of Cairns, and likely died of blood loss.
“We received a call about a 17-year-old with a serious upper thigh injury,” a Queensland Ambulance spokeswoman told AFP, adding that attempts to resuscitate him were made at the scene.
“A boat brought him in but he didn’t survive,” she added.
Queensland Ambulance Service executive manager of operations Greg Thiedecke said the boy went into cardiac arrest immediately after being bitten on his right upper leg, groin and upper arm.
“It would be speculating but (there are) a lot of large blood vessels in the groin area, so for him to go into cardiac arrest that quickly would be probably blood loss,” he told the Cairns Post.
Veteran diver Col McKenzie, who heads the Association of Marine Park Tourism Operators, told reporters Rudder Reef was not a common spot for dive tourism operators.
But he said it was popular with spear fishing enthusiasts, and there was a fatal shark attack at nearby Opal Reef almost a decade ago to the day.
Thiedecke said he grew up in nearby Cairns and he had not dealt with any shark attacks in his 25 years of ambulance duty “so it’s very rare”.
Experts say attacks by sharks, which are common in Australian waters, are increasing as water sports become more popular.
In October, a young surfer lost parts of both arms in an attack by two great white sharks off the south coast of Western Australia.
The most recent fatality was in September when a man was killed in front of his wife while swimming at Byron Bay on the east coast.