Checking the page, the female swimmer was horrified to find out the "creep" had indeed taken photos of her and shared it on Instagram.
"And on the story was yes me laying on my side with the gals out," she said, adding he had also included a shot of her butt.
During her time at the swimming spot, the woman said she had at one point turned on her side to check her phone without her swimsuit top on.
"When my chest is facing up to the sun, I'm usually wearing a cozzie top," she wrote.
"When I roll over to have my back in the sun, I take the cozzie off because ya know tan lines."
The woman said she has since contacted police and wanted to share her story so others knew.
"I want this to be a warning for anyone down in the Lilli Pilli area sun baking," she said, adding that the page has since been taken down after she and others reported it.
NSW Police said they are yet to receive a formal complaint but have called on anyone with information to come forward.
"There is no excuse for sexual offences, and it's time for the whole community to stand up and say it won't be tolerated at any time," they said in a statement.
