It was a hot day in January 2016, partway through the school holidays. Rebecca Hughes was fourteen, playing on the rocks at Merry Beach with two friends. They'd grown up by the ocean and they were careless, leaning into the spray of the surf, she says now.

When the water hit them, it knocked one of the girls into the swell. She struck her head on a rock on the way down.

Rebecca remembers seeing her bobbing face down in the water, thinking she was dead.

"Our other friend ran for help and I jumped in," she recalls. "I didn't think about it, I was just feeling the adrenaline. I needed to get her out."

As a dangerous rip sucked at their feet, Rebecca reached the girl and dragged her onto her shoulder.

She was still unconscious.

Each time Rebecca swam for land, both girls were flung out again, pulled beneath the surface or smashed back against the rocks. Underneath them was an underwater cave notorious for drownings.

"I thought this is it, we're both going to pass away," Rebecca recalls.

Eventually, Rebecca managed to push her friend onto the rock shelf and clamber up after her.

Help came a few minutes later, and both girls were rushed to hospital, covered in sand and shells and blood.

While her friend recovered from the bump to the head, the accident left her with a deformed toe. Rebecca's ankle bone was cracked and both girls cut down their sides.

"I was in so much pain, they were picking off little things like oysters and sand off us and blood was just rushing down our legs," Rebecca says.

"My mum cried when she saw me."

The girls returned to school still in their bandages.

"Word spread pretty quickly what had happened."

On Monday, Rebecca, now 17, will receive a commendation for her actions that day as part of the Australian Bravery Awards. Congratulating the winners, Governor-General Sir Peter Cosgrove said the country was fortunate to have so many Australians willing to put themselves in harm's way for others in need.

Rebecca now plans to join the Air Force when she graduates from Narrabundah College next year.

"I really hope no one makes the same mistake as us [that day] but it also gave me a taste of helping people, that's what I want to do."