Search for man after lewd exposure in the water at Half Moon Bay in Black Rock

Police have released images of a man showing his genitals to two teenage girls swimming at a south-east Melbourne beach in a bid to track him down.

The man entered the water around 2 p.m. on December 21 and approached the girls at Half Moon Bay in Black Rock.

He allegedly pulled down his black bathing suit and showed his genitals to the girls, who quickly swam away.

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The man then climbed out of the water and collected his belongings from a rock before heading to the rescue club.

On Monday, police released two photos and a computer-generated image of the man they say can help them with their investigation.

At the time of the incident, he was wearing a white hat, sunglasses, dark blue T-shirt, black shorts and work boots.

He also has a tattoo on his upper right arm.

Witnesses are asked to contact the police.