The family of a Victorian man who drowned while trying to rescue a child caught in a rip at a beach south of Sydney have paid to tribute to the father of three as a "larrikin" who would help anyone.

Shaun Oliver, 32, was found face down in the water after he swam out to help a 12-year-old boy struggling in the surf at Wollongong City beach about 4:30pm on Sunday.

The boy was one of four children who got into trouble in the surf. All four were eventually saved.

Mr Oliver's sister, Claire Murray, said her brother would help anyone who was in trouble.

"He'd stop on the side of the road and change a tyre, he was just that kind guy and everybody loved him, he was a practical joker," she said.

"I'm waiting for this to be practical joke, but it's not.

"If there was a bigger word than hero, that's what he would be.

"We're so devastated … we just don't know what we will do without him."

Father of three, Shaun Oliver, was remembered as a practical joker. ( Supplied: Facebook )

Amy De Battista, another sister of Mr Oliver, said the good Samaritan had " given the ultimate sacrifice".

"This is how we were brought up, we help people that's what we do. So if someone's in need, we do our best," she said.

Friends and family of Mr Oliver have paid tribute to him on social media.

A crowd funding page on the GoFundMe website has been set up to help his wife and three children.

Mr Oliver has been remembered as a keen sportsman and played as a junior and senior at Keysborough Football and Netball Club.

Police said Mr Oliver and others who tried to save the four children had shown "remarkable acts of bravery".