The body language is more subdued in the camp gathered a few metres back, in the ranks of off-duty lifesavers who had come to the girl's aid, launching a mass, after-hours rescue when she and six friends - visitors from Fairfield in Sydney's west - were swept suddenly out to sea.

Adam Turner was the first to raise the alarm. He lives nearby and had come to the water hoping for an after-work swim. He grabbed some flippers when he saw the group being swept away in a line and flagged down a skilled nipper he recognised, telling him, "mass rescue, we need to get out there".

Mr Turner said the swimmers had been standing in quite flat, waist-deep water and "seemed alright" seconds before a succession of waves came and claimed them.

"It was a good demonstration of how quickly it happens," he said.

"They went from that sand bank to that rip in three seconds - 'bang, bang, bang'. The power of those three waves literally just lifted all seven of them up and threw them straight across into that trench."

"There's a trench there - that's why it's ripping. See how the water looks like it's pulling backwards? It's darker and the waves are struggling to come in? That's your classic rip. At Austinmer it goes round the back of the rocks and that's the problem, because the next wave comes and slams you across the rocks."

Mr Turner pays tribute to another three rescuers who helped him bring the stricken group safely to shore.

Multiple police cars and ambulances rushed to the beach after one in the group - the girl - went repeatedly underwater. Turner worried she was at risk of "secondary drowning" - where even a tablespoon of seawater, ingested, can claim a life. He tells the Mercury this but it falls to Austinmer club captain Alistair Reid to reveal one of the most significant aspects of MrTurner's rescue effort - this was the fourth he'd stumbled into this week - the latest of 18 people he has helped bring to shore at Austinmer outside of patrol hours, or at nearby Sharkey's Beach in Coledale - an unpatrolled beach.

"The 18 people [rescued with Mr Turner's help] this week - all of them have the same theme: no flags were up, and they were all looking at the bit of the beach that doesn't have waves and thinking, 'that's safe'," Mr Reid said. "When you grow up at the beach in Australia you swim between the flags and you don't go where the water's green because that's where the rip is."

Surf Life Saving Illawarra duty officer Daren Weidner believes the region is witnessing a boom in beach visitors due to travel restrictions associated with the coronavirus pandemic. He led a debriefing session for his off-duty patrol members after Monday's rescue, acknowledging it would unlikely be the last one this summer.

"Unfortunately this is happening regularly, and with the Australia Day weekend coming up the forecast is for very warm wether and some solid swells," he said.

"We just need to make sure people are swimming between the flags and not swimming alone or out of their depth."