A young couple from Switzerland were filming dolphins in the water off a NSW beach when a shark attacked them, killing a woman and leaving a man with serious injuries as he tried to fight it off.

Emergency services were called to a beach at Crowdy Bay near Port Macquarie – an unpatrolled beach known to be a shark hotspot about 6.30am yesterday.

Bystanders from a nearby campsite provided aid to the victims before paramedics arrived but the woman, believed to be aged 25, died at the scene.

The pair were trying to film a pod of dolphins before the shark attacked. The pair were trying to film a pod of dolphins before the shark attacked. (Nine)
A woman is dead and a man injured after a shark attack on a Mid North Coast NSW beach at Crowdy Bay. (9News)

The woman’s boyfriend, a 26-year-old man, was airlifted to John Hunter Hospital with serious injuries.

He remains there today in a serious but stable condition.

It’s believed they were mauled by a three-metre bull shark.

Ambulance Superintendent Joshua Smyth praised a bystander who applied a makeshift tourniquet to the man’s leg, saying they “potentially saved his life”.

The man was hoping to film his girlfriend interacting with a pod of dolphins before she was believed to have been attacked by a shark.

Bull SharkExperts are exploring theories they were mauled by a three-metre bull shark. (Getty)

Police are now reviewing GoPro footage the couple recorded which 9News understands shows dolphins in the water, just prior to the attack.

Today was supposed to be the last day of the pair’s Australia trip before they caught a flight back to Switzerland this afternoon.

Beaches remain closed

Multiple beaches have been closed, with Surf Life Saving working to secure signage to let beach-goers know ahead of an anticipated hot weekend.

There will be extra surveillance at patrolled beaches on the weekend.

It’s not known when the closed beaches will be reopened, though it is believed it could be for at least a few days.

Crowdy Bay is a remote part of NSW. (Getty Images/iStockphoto)

Surf Life Saving NSW chief executive Steven Pearce told 2GB the association was sending up surveillance drones and personnel to support police and the Department of Primary Industries.

“These incidents are horrific for everyone, and unfortunately we’ve had a few this year,” he said.

“This area, it’s just so remote, you know, there’s no lifeguarding service up there at all.”

A report will be prepared for the coroner.