A recreational scallop diver was killed in front of his daughter by what is understood to be a great white shark off Tasmania's east coast.

The attack happened between Lachlan Island and Maria Island near the coastal town of Triabunna.

Inspector David Wiss from Tasmania Police said the man, in his late 40s, and his daughter were diving from their small aluminium dinghy about 8:00am when the attack happened.

"My understanding is the daughter returned to the boat and the father returned to get some more scallops," he said.

"He did not return to the surface.

"His daughter became worried and went down and checked on her father."

The young woman in her 20s "saw a very large shark and she saw her father being attacked by the shark".

"She immediately returned to the surface where she raised the alarm through setting off a flare and also by making an emergency phone call."

He said nearby fishermen were alerted by the flare and went to offer assistance.

"Boaters attended the area and they pulled up a male using the air hose he was attached to but unfortunately he was fatally injured," he said.

"This is a deeply traumatic incident for the daughter.

"We're providing support as best we can [and] we've got professional critical incident people attending their residence as we speak."

Sorry, this video has expired The victim spotted the shark but was unable to return to his boat

John Hammond from the Scallop Fishermen's Association of Tasmania said he was shocked by the news.

"[It's an] absolute tragedy for the family. Bloody terrible," he said.

"From what I understand his daughter was swimming with him so it would just be horrendous for [her]."

Mr Hammond said there were a number of other divers in the water at the time of the attack.

"[The diver was] in the shallow water there, it just struck out of the blue, and bang," he said.

The boat has now been returned to the wharf in Triabunna.

Recreational diver Simon Cornelius was in the same area only a short time before the attack.

"It's a bit sickening," he said.

"You've just been in the area and it could have been you.

"I won't be going back in a hurry that's for sure."

Great white 'cruised past' diver less than 24 hours earlier

Glamorgan Spring Bay Mayor Michael Kent said the area was not known for sharks but a "15 foot [4.5 metre]" animal had been spotted in the area a number of times in the past week.

"There's been a so-called white pointer seen a couple of times over the last week out and about but [there is] not particularly a lot of sharks in and around that particular area," he said.

"I don't know how long the shark's been in the area.

"I've been told about a week."

There were a number of people diving for scallops in the area at the time of the attack. ( ABC News: Andrew Fisher )

Diver Danny Smith said he was in the water with a friend near Lachlan Island on Friday afternoon when he saw a shark about four to five-metres long.

"I got three metres off the bottom and got tapped on the shoulder, so to speak," he said.

"I thought it was my mate and I turned around and looked at ... what I said was a 14 to 16 foot great white.

"It had no intention of biting me, I believe, it just sort of cruised past to see what I was."

Mr Smith said he got back to the boat, raised the alarm and he and the other crew members started pulling his diving buddy back to the boat.

"The [shark] came to the surface to see where I'd gone I presumed and she sort of took a swipe at him," he said.

"We saw fins and arms and legs going everywhere, we were initially thinking that we were going to pull in half a body.

"We got him on the boat and she came right to the back of the boat and then just descended back to the bottom."

Community 'shocked and devastated'

The last fatal shark attack in Tasmania occurred 22 years ago near Tenth Island off the state's north coast.

Mr Kent said members of his community are "devastated".

"We pour out our sympathy to the family and from a council perspective if there's anything that we can do to assist in any way, shape or form we are only too happy to do so," he said.

"The people I have spoken to, they are in shock some of them, devastated."

Mr Kent said it was the last weekend for divers to take advantage of scallop season which ends on Friday.

"The scallop season has been one of the best for amateur and professional fishermen for some time so it's created more people diving," he said.

Boat owners have been warned to stay clear of the area.