A near-naked man was filmed taking a dip in the Sydney Zoo aquarium in the west of the city.
Video shared on social media shows the man in his underwear swimming amongst the fish.
Jake Burgess, managing director of Sydney Zoo, slammed the man’s actions.
“We are completely appalled people are behaving this way,” Burgess told 7NEWS.
“It not only jeopardises their own safety but that of the welfare of our animals as well.”
NSW Police are investigating the incident and it has been referred to the RSPCA.