Around 6.45am March 13 NSW Ambulance were called to Merimbula's Main Beach after reports a woman had been struck in the back, with reports from someone at the scene saying it was a shark..

The 63-year-old woman was treated for superficial puncture wounds in the shoulder, back, hip and buttocks an Ambulance spokesman said on Saturday morning.

She was taken to South East Regional Hospital in a stable condition.

"There was initially some uncertainty if it was a shark, bystanders on scene reported seeing fins and a large animal," NSW Ambulance Inspector Robert Whitney said.

"It was pretty clear that it had been a shark attack as paramedics arrived on scene."

"What we could see is that the patient suffered multiple wounds in what would have been a terrifying event, paramedics did a fantastic job in treating the patient down at the beach before transporting to hospital."

Both Merimbula and Pambula beaches were closed Saturday after the incident.

The Dorsal app reported sightings of both a tagged bull shark at Merimbula Main Beach around 4.46am and an unknown species at 8.05am.

Department of Primary Industries experts are investigating and are yet to advise on the type and size of the shark involved.

Surf Lifesavers will work with the Bega Valley Shire Council to close beaches in the area for the next 24 hours, from Wallagoot Lake down to Pambula.

Surf Life Saving drones will launch this morning to conduct surveillance of the waters off Merimbula and will work with the DPI to monitor any marine activity.