Teen In Critical Condition After Northern Territory Shark Attack

Medical staff believe a teenager who suffered serious injuries after being attacked by a shark off the NT coast will likely survive and keep his injured arm but he remains in a critical condition following surgery.

Sean Whitcombe, 17, was spearfishing around 40km offshore of Nhulunbuy in the Gulf of Carpentaria when the attack occurred on Sunday morning.

He was in about five metres of water and is believed to have been bitten on his arm and leg while coming to the surface after spearing a fish.

Whitcombe told medical staff he had been mobbed by numerous sharks.

The main injuries were significant bites to his upper left arm that damaged blood vessels and could easily have killed him, given how much blood he lost.

His friends including an Aboriginal trainee nurse have been hailed as heroes after administering first aid by wrapping clothes and towels around him as a tourniquet to reduce the profuse bleeding and trying to keep him calm.

The group also had an emergency radio beacon (EPIRB) although it took two hours for police to arrive.

Top End Health surgical executive director Mahiban Thomas said he was confident Whitcombe would survive and keep his arm but it was too early to tell what permanent damage there was.

"That is a very lucky young man who was exceptionally well supported by his friends who are to be commended for excellent work keeping him conscious and keeping his blood loss down ," Dr Thomas told reporters.

"It was very fortunate there was a health practitioner on board and they have managed to preserve his blood volume until he was in much better care.

"He certainly would've died if both the emergency response, intermediate response and final reaction from Royal Darwin Hospital had not been as polished as it was."

Whitcombe was due to have another operation on Monday following emergency surgery on Sunday after being airlifted 1000km from Nhulunbuy to Darwin.

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He had lost a significant amount of tissue, suffering vascular injuries including damaged blood vessels that had been repaired through very complex surgery, Dr Thomas said.

He said in his 15 years in the NT the man was the first shark attack case he'd treated.

In September, a 17-year-old boy was bitten by a bull shark off nearby Groote Eylandt, while there have been numerous attacks around Australia in the last two months.