Two brothers are recovering in hospital after being injured by a marlin in a bizarre boating incident on the north coast of New South Wales.

Key points: The men were boating in the Solitary Islands Marine Park when the incident occurred

The men were boating in the Solitary Islands Marine Park when the incident occurred They were both treated for their injuries at Coffs Harbour Hospital

They were both treated for their injuries at Coffs Harbour Hospital A fishing charter boat operator said the men were lucky to be alive

The men, aged 46 and 48, were fishing with a third man from an inflatable boat in the Solitary Islands Marine Park off Coffs Harbour about midday when a large marlin breached the water and landed in the vessel.

Westpac Rescue Helicopter aircrew member Michael Kerry said the fish — weighing up to 100 kilograms — seriously injured one of the brothers.

Both were "really shocked by the bizarre incident," he said.

"The gentleman who was closest to the fish saw it at the very last moment and put his arm up to protect himself, and mainly his head, and that's when the fish has impacted and caused most of the damage.

"He has a very deep laceration to that arm as well as fractures."

Mr Kerry said the other brother saw the fish coming and managed to turn away in time but still suffered puncture wounds to his back.

The 46-year-old was flown to Coffs Harbour Hospital and was in a stable condition, while his older brother was taken to same hospital by road.

Mr Kerry described the incident as a "dangerous situation" and said the men were "in the wrong place at the wrong time".

"You're talking quite a big thing they're being hit with," one charter boat operator said. ( File )

"It's not every day you get hit by a marlin," he said.

"Talk about the fish that got away.

"It all happened so fast that they didn't really know what had happened to them.

"All they saw was this big fish jump out of the water and hit right into them."

Mr Kerry said the incident was "one of the most unusual jobs I've ever been to".

'They're lucky they're alive'

Stan Young from Wooli Fishing Charters said it was a fluke accident.

"They're lucky they're alive, especially the guy that got speared in the shoulder and come out the other side of him — terrible," he said.

"It's like being stuck with a sword.

"You're talking quite a big thing they're being hit with, and on top of that you've got the fish going off its brain at the same time it's inside this poor bloke.

"It would have been mayhem. It would have been terrible."