Shellharbour beach in New South Wales (Google Maps )

A married British couple have drowned after getting into difficulty while swimming off the coast of New South Wales, authorities have confirmed.

The couple, aged 66 and 64, were visiting family in Australia when the tragedy unfolded on Wednesday, March 11.

Emergency services were called to Shellharbour Beach at Shell Cove, about two hours south of Sydney, shortly after 11am following reports that two swimmers were struggling in the water.

Beachgoers pulled the man, 66, and the woman, 64, from the surf after noticing they were in distress.

Off-duty nurses at the scene immediately began performing CPR before paramedics from NSW Ambulance arrived and took over.

Despite their attempts to resuscitate the couple, they could not be revived.

It is understood members of the couple’s family were present at the beach at the time of the incident.

More than a dozen first responders remain at the scene, with images showing privacy tents set up on the beach to shield the area from public view.

Witnesses said a large multi-agency emergency response was deployed, though the atmosphere remained calm as those at the scene worked urgently to try to save the couple’s lives.

“It was pretty calm, everyone knew what they were doing. It wasn’t a made panic, everyone just switched into what they were doing,” a beachgoer told the Illawarra Mercury.

“It puts it all into perspective how quick things can go wrong.”

New South Wales Police praised the quick actions of two off-duty female nurses and a young man who helped bring the swimmers to shore and assisted with first aid.

A police spokesperson said: “This is a tragic incident and our hearts go out to the family.”

It is understood the beach was not patrolled by lifeguards at the time.

A report will be prepared for the coroner.