The Wanda Beach murders and the 15-year-old girls we must never forget.

On January 11, 1965, best friends and neighbours, Marianne Schmidt and Christine Sharrock, disappeared at Wanda Beach in Cronulla. They were just 15 years old.

The next day their bruised, battered and slashed bodies were found on the beach, partially covered by sand. More than 50 years later, no one has been charged with their murders, and their untimely deaths still haunt the shire community.

On the day of their disappearance the girls headed down to Wanda Beach, a small and isolated stretch in the Sydney suburb of Cronulla, with four of Marianne’s younger siblings in tow.

When they reached the beach they found it was closed due to windy weather, so they sheltered in the nearby rocks.

The littlest Schmidt boy, Wolfgang, still wanted to swim so Marianne took him down to the shallow water away from the rocks. After a little while they returned to the group and they all had a picnic together.

At some point during the picnic, Christine wandered off. No one knows where she went or what she was doing during that time, but after her death it was discovered she had consumed some alcohol and eaten some different foods to the rest of the group.

Around this time, eight-year-old Wolfgang noticed a boy hunting crabs. He said he saw the boy two more times - once with the two girls and another time walking alone.

However, Wolfgang has never been able to give an accurate description of the male, claiming at one time that he was carrying a homemade spear and at another time, a knife.

Around 1pm the group decided to go for a walk into the sandhills behind Wanda Beach. About halfway through their walk, the girls told the younger kids to wait while they headed back to the rocks to collect their bags and belongings.

According to the Casefile podcast, the girls then headed further into the sandhills and laughed when the kids told them they were going the wrong way.

That was the last time the four Schmidt siblings would see Marianne and Christine alive. They waited in the sandhills until 5pm, before collecting their belongings and heading home. At 8.30pm that night, the girls were reported missing.

The last person to see Christine and Marianne was local fireman, Dennis Dostine.

Dostine was walking with his son in the area when he spotted Christine and Marianne walking about 700 metres north of the surf club. He said the girls looked like they were hurrying and one of the girls was looking over her shoulder, like she was being followed.

The next morning, local resident Peter Smith was taking his three nephews for a walk when he discovered what he thought was a department store mannequin buried in the sand.

But it wasn't a mannequin - when Smith brushed some sand off the hand he realised it was a body. Police were called from the surf club and when they arrived they discovered the bodies of the two young girls in the sand.

Christine's skull had been fractured and she had been stabbed multiple times, a long drag mark indicated that she may have tried to flee as Marianne was murdered.

Marianne's throat had been slashed. The murderer had attempted to rape both of the girls.

Police were never able to locate the murder weapons and while a number of suspects were investigated, no one was ever charged with the crime.

According to The Daily Telegraph the lead suspect, child killer Derek Percy, died from cancer in 2013. While police hoped Percy would give them a deathbed confession, he remained tight-lipped until he took his last breath.

The case was reopened in 2007 and 2011 when police tested DNA from a possible knife wipe on one of the girls' clothing, but so far the results have been inconclusive.

Investigators are still hopeful that improvements in DNA testing will finally help them crack the case that has haunted the beachside community for over 50 years.

Until that day comes, we need to remember Marianne Schmidt and Christine Sharrock.

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