They headed out in darkness to a duck pond with a jet-ski, hoping to have a quacking good time. But a group of young men have raised the ire of Helensburgh residents, who have labelled the stunt "stupid" and "disrespectful".
Several residents living near Helensburgh's Gymea Glade duck pond and park awoke around 3am on Sunday to the sound of a motor turning over.
Outside, they saw a jet-ski lapping the shallow suburban pond and a group of laughing men.
Resident John Hill took to a Helensburgh community Facebook page to complain about the prank, which he said was inconsiderate and disappointing.
"Not only was it an outrageously anti-social act because of the noise, but for those of you who take your kids there to feed the ducks, imagine how these dropkicks terrorised the large numbers of water birds that live there," he wrote.
"If you own this goose, if he is your son, or brother or God forbid your husband, tell him to wake up to himself."
The group, who used a large ute to tow the jet-ski through the park and launch it into the pond, rode the watercraft for more than 30 minutes.
Residents said they often found alcohol bottles and litter left over from late-night parties in the park.
Ward 1 councillor Greg Petty said he planned to act on complaints he received about the incident and that he was fed up with antisocial behaviour in the northern suburbs community.
"As a resident myself I'm seeing it far to often - the antisocial behaviour, the alcohol-fuelled violence and stupidity. I don't understand people who seem to think it's acceptable behaviour," Cr Petty said. "The saddest thing is people on the Facebook site appear to be condoning such outrageous behaviour."
Some commenters on the Helensburgh Cheersandjeers page laughed and commended the stunt, while others such as an Otford environmentalist raised concerns about the safety of wildlife at the pond.
"Since the pond was constructed to control stormwater and debris from entering the Hacking River, it's also become home to native grey teal ducks and other native birds," Natasha Watson, a WIRES volunteer, said.
"I know 'men will be boys' but have some consideration for the neighbourhood and environment."
Neighbourhood Forum 1 co-convener Warwick Erwin said he would raise the incident with police.