A shark that “grabbed” a 10-year-old boy from a fishing boat off the coast of north-west Tasmania “swam off” when the child’s dad jumped in the water to save him.

Authorities said the boy was in a 6 metre fishing vessel with his father and two other men on Friday afternoon when the shark “grabbed him from the boat”.

The child suffered lacerations to his arm, and other cuts to his chest and head.

The child, from north-west Tasmania, was this in a stable condition at the North West Regional Hospital, before being transferred to the Launceston General Hospital on Friday evening.

Stanley resident and abalone diver Ben Allen was at a nearby boat ramp when the party made it back to shore.

He spoke to witnesses and said the shark was believed to be a great white, but that has not been confirmed.

Mr Allen told ABC Radio Hobart the family was cleaning flathead on the boat when the attack occurred.

“All of sudden, the shark’s leapt clean out of the water and it’s grabbed the little boy and pulled him straight in,” Mr Allen said.

“But as he’s pulled him in, it’s obvious the shark’s let go.

“The father, with his natural instinct I suppose, has leapt in straight after his son and managed to grab him.”

Mr Allen said the boy has “got something to tell the kids when he grows up”.

“Congratulations to dad. Top fella, it just a very very scary thing.”

“It is obviously a freak accident and I really do feel for the family — it could have been a lot lot worse … buy a lottery ticket, I think.”

Scenic Stanley is postcard beautiful, but death lurks in the waters. Photo: Discover Tasmania

He said a friend of his administered first aid, and the boy was rushed into a nearby seafood shop to keep him dry and warm until the ambulance arrived.

“All the boys said [the shark] was big, I imagine it was very big. It is renowned for this time of year that they do go in that area,” he said.

Mr Allen believes the shark would have been “in feeding mode”.

“We have a seal rookery nearby, that’s obviously where they are feeding.”

He said there had been “a couple of divers of late that have been bailed up on the bottom and they’ve said [sharks] have not been aggressive so he was obviously ready to feed … it’s just the time and place that you are obviously encountering”.

“It’s their area, you’re in their domain, it’s just mother nature, its one of those things.

“You’ve got to accept the consequences. We are in the water two or three times a week diving and me, personally, I haven’t seen one, but I’ve got a lot of good mates that have seen them,” Mr Allen said.

Cleaning fish likely trigger

Shark attack researcher and author Chris Black said it was likely the shark was spooked by the father’s action.

“It was probably the last thing it expected,” he said.

“White sharks, of all the shark species, are the only ones which will elevate their heads above water to check out what’s happening on boats.

“If they had been cleaning fish off the side of the boat, then clearly that’s put entrails into the water that a passing shark will react to.

“It’s in the DNA to investigate any source that could be food for them.”

Mr Black described the incident as a “very rare occurrence”.

“That shark, I can only stress again and again, was only doing what is natural to it.”

Tasmania police had issued an alert just before 2:00pm on Friday warning of a “large shark” sighting approximately 10 kilometres off the coast of Stanley.

It warned anyone swimming or undertaking any other marine activities to “take necessary precautions”.

In 2015, a recreational scallop diver was killed in front of his daughter by what was understood to be a great white shark off Tasmania’s east coast.

-ABC