The damage is believed to have occurred on Thursday evening, just hours after signs were erected providing information on recommended safe swimming areas.
Queenstown Lakes district harbourmaster Marty Black reported the damage to police yesterday and said the culprits faced a $500 fine for damaging maritime safety equipment.
"Someone must have seen something. That is definitely sawed," Mr Black said, pointing to the surfaces on the plastic loops. Fortunately, he already had "quite a swag of new buoys" because he had planned to extend the line further south by about 200m yesterday. More buoys would have to be bought.
The buoy line had been installed about three years ago and each buoy cost $20-$25, he said.
Sgt Aaron Nicholson said yesterday the damage was "mindless" and would be investigated.
He asked for public help with information.
Wanaka Lake Swimmers Club president Claire O'Connell has lobbied for years to have the safe swimming zone clearly marked, with the aim of reducing conflict between water-user groups.
"It just seems absolutely ridiculous. You would have to wonder who would want to do something like that.
"What the harbourmaster is trying to do is set up a safe swim area and someone has gone and cost the community a lot of money by sheer vandalism," she said.
The Stoney Creek swim zone is accessed from a car park on Mt Aspiring Rd and is in frequent use by swimmers training for Challenge Wanaka on January 21.
The two other Roys Bay safe swimming zones are in front of the log cabin, accessed from Ardmore St, and in front of the scout den, accessed from Eely Point. Bremner Bay is also a safe swimming zone.
