Two teenagers were treated by paramedics after they became stuck in a strong rip at Bulli Beach.
They were among a group of five teens who were swimming at the southern end of the beach around 5.10pm, on Tuesday, September 20.
"A number of males were struggling in a strong rip current on the northern side of Woonona Pool," Surf Life Saving Illawarra's Anthony Turner said.
"A board rider saw the commotion and brought the person struggling the most back into shore, and the others self-rescued."
The teenagers were all from Moss Vale in the Southern Highlands.
"They were probably a little bit unfamiliar with conditions and things can change dramatically in the ocean," Mr Turner said.
He urged people to watch out for their mates if they're going swimming.
"Know your limitations and abilities in and around the water," he said. "Supervise children at all times.
"Always swim at patrolled beaches between the red and yellow flags."
Surf Life Saving patrol season begins on September 23, and Mr Turner said this rescue was a timely reminder of the dangers of swimming at unpatrolled beaches and how things can change quickly in the surf environment.
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