Police are examining whether a Swiss couple were using a GoPro to capture footage of dolphins when a shark fatally mauled one of them at a remote NSW beach.

A 25-year-old woman died and her boyfriend suffered serious leg injuries in the incident at Kylies Beach in Crowdy Bay on the Mid North Coast on Thursday morning.

The 26-year-old man is believed to have tried to fight the shark off before dragging his critically injured partner back to the sand on the unpatrolled stretch of coast.

A beachgoer spotted the pair and called triple-0, following instructions from paramedics to fashion a tourniquet on the man’s thigh, which is thought to have stemmed heavy bleeding. Paramedics were unable to save the woman, who was pronounced dead at the scene.

Her partner was winched into a Westpac rescue helicopter and taken to John Hunter Hospital in a critical condition, but has since improved to a serious but stable condition.

The pair, who were holidaying from Switzerland, had been swimming and filming dolphins on a GoPro, which may have inadvertently recorded the moment the shark struck.

Detectives are expected to analyse the footage to determine the species involved, with shark experts saying the injuries are consistent with a mature bull shark.

Kylies Beach, a secluded coastal strip near a popular campground and without lifeguard patrols, remained closed on Friday.

The couple had checked into the nearby campsite on Wednesday and were believed to be travelling in a hire car from Queensland, with local beaches now shut until further notice.

The couple is yet to be identified, with NSW Police preparing a report for the coroner.

NSW Ambulance Superintendent Josh Smyth labelled the event “tragic” and praised those who rushed to help.

“I need to (give) a shout out to the bystander on the beach who put a makeshift tourniquet on the male’s leg (which) potentially saved his life and allowed NSW Ambulance paramedics to get to him and render the first aid,” he told reporters.

“The courage from some bystanders is amazing in the situation and … to put yourself out there is very heroic. The community … rely on those things.”

In response to incidents like this, Australian surfer Danny Schouten is spearheading an initiative to deploy life-saving shark bite kits on beaches nationwide. These kits, designed to control severe bleeding after shark attacks, have already been installed on more than 150 beaches across NSW, Queensland, South Australia, and Western Australia.

Mr Schouten, joined by shark attack survivors Toby Begg and Kai McKenzie, who inspired the project after their own experiences, is currently fundraising via GoFundMe to expand the rollout.

“When a shark attack happens, every second counts. A Shark Bite Kit provides tools that can help control bleeding and hopefully increase someone’s chance of survival. With the support of communities and donors, we can get shark bite kits on every beach around the country,” Mr Schouten said.

Mr Begg added, “Shark bite kits are important because they have the potential to be life saving specifically to stop massive bleeding until emergency help arrives. I know from my own experience that the application of a tourniquet and having the means to manage a traumatic situation could make all the difference when seconds count.”

Meanwhile, McKenzie said, “The shark bite kits are a great idea that could really save someone’s life. I was lucky to have someone with such experience to save me, but there will come a day where that won’t be the case and a Shark Bite Kit would help the chances of surviving dramatically.”