Police have revealed they are searching for the remains of Tathra resident Christine Armstrong, who they think was attacked by a 3-4m shark while taking her daily swim near Tathra jetty.

The former Canberra woman, who went to Girls Grammar, had been swimming with a group, but was attacked after turning back on her own about 8.20am.

Poor visibility has forced authorities to call of the search for her remains for the day. They will resume at dawn on Friday, but a police spokesman warned it could be days before her body was recovered if it has sunk below the surface.

Mrs Armstrong's family has issued a statement saying she had been swimming at Tathra for many years.

"Chris was very loved by many people. She has been swimming at Tathra Beach for 14 years and was an experienced and committed member of the surf club," the statement read.

"She was a senior surf club trainer for many years and swimming brought her much joy and many friends. She will be sadly missed by all who loved her, especially by Rob, her husband of 44 years."

Mr Armstrong was one of the group of five swimmers, who said they saw a large shark in the area. Another man also reported seeing a shark from rocks nearby. Tathra Beach has been closed following the fatal attack.

The shark attack comes just two years after Tathra Surf Life Saving Club's then-surf boat captain Sharon Clarke warned shark fishing off the wharf was attracting sharks to the area.

The small coastal town is no stranger to tragedy.

A 19-year-old Bega man drowned near Tathra in October 2013 after he was caught in a strong outgoing current. His body was later found by whale watchers near Eden.

Shane O’Neill, a 28-year-old Butcher from Kalaru, drowned at the Tathra Wharf in November 2008 after diving into the water to save his two sons who had fallen five meters into rough seas.

Police said the people who had been swimming with Mrs Armstrong were treated for shock and were under general observation.

"Emergency services are doing what they can for them but naturally they're shocked and horrified by what’s occurred," said a police spokesperson.

Two surf lifesaving vessels, along with local fishing vessels under the co-ordination of NSW Water Police, were also looking for the shark.

Westpac Lifesaving operation manager Craig Roberts said the Lifesaver 3 helicopter had been unable to spot the body and police stood down the helicopter at 12.42pm.

Police initially gave the helicopter a search area north and south of the Tathra headland.

Mr Roberts said the helicopter had dropped dye into the water to determine the flow of the tide.

Tathra residents have spoken of the loss of one of their own.

Bega District News editor Ben Smyth said it came as a shock to locals.

Tathra woman Molly Carroll, who was on the beach just minutes before the fatal attack, described the scene as "eerie".

"It is a bit of a shock," she said.

"It is a bit of an eerie feeling."

Bob Armstrong has spent 60 years in Tathra and has had a long association with the local surf life saving club.

He said that in the 1950s, the club patrolled around the cliffs and had seen sharks in the area but this was the first attack in the area he knew of.

The alert went out shortly after 8.40am on Thursday, with police, surf lifesavers, the ambulance service and the Lifesaver 3 helicopter called to the scene.

It is understood Department of Primary Industries fisheries officers will conduct an investigation at Tathra once the shark attack is officially confirmed.

The woman's death is the second fatal shark attack in NSW waters in five months.

Zac Young, a 19-year-old body boarder died, after he was attacked by a tiger shark at Campbell's Beach north of Coff's Harbour on November 20 last year.

Two other men were bitten by sharks in separate incidents in the past 12 months, but neither were seriously injured.

- with Bega District News and Fleta Page