A woman whose heart stopped beating in the surf at a popular Sydney beach has lent her support to a new drive to train more CPR responders.

Cassandra Scott was out in the surf at Coogee beach 18 months ago when another swimmer found her floating face down.

Dragged back to the sand, four total strangers spent the next 15 minutes frantically at work.

"My heart was lifeless but then it just suddenly started," she told AM.

"And I'm also told that it was very unusual in that after a time people give up, but that I was being given CPR by someone who'd just done their training and so they just kept on going. And, against all the odds, I came back to life."

Ms Scott was one of the lucky ones.

In Australia, less than one person in 10 survives a cardiac arrest but elsewhere up to 50 per cent of patients have successfully revived.

According to estimates, 20,000 to 30,000 Australians die from cardiac arrest every year.

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New organisation Take Heart Australia is now hoping to improve the nation's cardiac arrest survival rate.

The group is headed by associate professor Paul Middleton, an emergency medicine expert who divides his time between research, teaching and frontline work at Sydney's Manly Hospital.

"Every single person has the tools to save a life at the end of their arms, basically," he said.

"If we can get 50 per cent of our population trained in CPR, at recognising cardiac arrest, and we have defibrillators everywhere that are linked to the triple-0 number so that operators know where they are as, well, I think we will save thousands of lives in Australia."

Associate professor Middleton said the US city of Seattle set the benchmark, with 56 per cent of patients surviving.

"They've got something like 75 per cent of their whole community trained in CPR," he said.

"There's a joke that you can't fall asleep in a park in the summer in Seattle because somebody will start doing CPR on you."