A renowned beach scientist has warned that unpredictable ocean swells could fool even the saltiest of Illawarra residents, during a public seminar on Thursday.
Dr Rob Brander, or Dr Rip, spoke to a packed room at the North Wollongong Surf Life Saving Club about the dangers of rips, how to spot them, and what to do if you're caught in one.
Dr Brander's core message was "white is nice, but green is mean" - a reference to the deep green colour created when rips form.
He said the most important rule for people to remember was to swim between the flags.
However, he said not all rips were the same.
"Most rips sit in deep channels between sandbars.
"The deeper they are, the more they look like dark green gaps going out through the white water. Often rips look like the safest places to swim."
Dr Brander began conducting his public educational talks 10 years ago after moving to the Illawarra and volunteering as a lifesaver.
"A lot of people we were rescuing were locals and they didn't understand how things worked," he said.
He said the best piece of advice for anyone caught in a rip was to sit back and relax.
"Don't panic," Dr Brander said.
"If you get caught stay afloat, relax, and signal for help.
"If help doesn't come ... swim to where the waves are breaking."
During the presentation, Dr Brander used purple-coloured dye in the ocean to demonstrate how currents could pull a person out to sea in a matter of seconds.
He said, as a general rule, rips were faster within two hours either side of low tide. The biggest myth about rips was they could pull people under, and they all pulled people out to sea.
"They all behave differently. Just stay afloat."