Eighteen people were rescued on Queensland's Gold Coast after a sandbar collapsed in a strong rip which carried some swimmers 100 metres out to sea on Sunday.

Surf Life Saving Queensland said the sandbar, about 40 metres offshore at North Burleigh beach, had become too soft in its foundations and gave way in the force of the water.

Twenty people lost their footing and suddenly found themselves in deep water.

Beachgoers leapt to help two young children before they were taken too far offshore.

They were brought in on boogie boards.

Another 18 people began drifting out to sea and five lifesavers started their mass rescue operation, without the aid of a boat.

Patrol Captain at North Burleigh, Jeff Hutchison, said rescuers remained calm as some of the swimmers panicked.

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"They panicked that they couldn't feel the bottom anymore and they are getting sucked further and further out to sea," he said.

"Once our members got to them with boards and tubes and they know they can stay up (they stopped panicking).

"We took control of the situation, which lasted about 10 minutes.

"The patrol members are trained and did their job well."

A backup was called in from nearby Miami, but all swimmers had been rescued by the time it arrived.

Mr Hutchison said it was the biggest rescue North Burleigh had seen this year.

"But it is not unusual for a bank collapse and many people need rescuing," he said.

He was disappointed that once the rescue operation was complete, beachgoers returned to the sea.

Another four people got caught in a rip and had to be rescued.