Detectives were told the boy managed to get away from the unknown man and raise the alarm with nearby adults at South Terrace on Saturday morning.
It is understood the boy went to the bathroom at about 9.30am when he was allegedly approached by the man.
The toilet block was metres from the cricket pitch and next to a playground full of young families.
“It’s the last thing on your mind, kids are playing, it’s such a safe area, such a safe place,” one parent told 9News.
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“You can’t even imagine that something like this would happen.”
Police and police dogs searched the parklands but were not able to locate the suspect, who is described as Caucasian and disheveled looking with an orange beard and dirty straight hair in a mullet.
Detectives are speaking with witnesses and collecting evidence as investigations continue.