Lake Hawea assistant harbourmaster and marine search and rescue team member Trev Hewson checks the Niwa wave-measuring buoy in the lake yesterday after a concerned resident reported it to the police on Sunday night. Photo by Marjorie Cook

Police and search and rescue leaders are reassuring the public this week there is nothing untoward about a light that flashes constantly on Lake Hawea at night.

The flashing white light is attached to a large wave-measuring buoy belonging to the National Institute of Water and Atmosphere and Contact Energy.

It is part of Contact's resource consent monitoring requirements, and gathers data on height, direction and frequency of waves and should be removed by the end of March.

It has sparked four callouts to police and search and rescue leaders since it was put in the lake at the end of November.

Senior Sergeant Allan Grindell confirmed yesterday the most recent call was made to Wanaka search and rescue co-ordinator, Sergeant Aaron Nicholson, about 9.30pm on Sunday.

The call came from a Lake Hawea resident who had never seen the buoy before and had noted a repeated pattern of five flashes followed by a pause, Snr Sgt Grindell said.

Queenstown Lakes District Council harbourmaster Marty Black said yesterday he was aware of another call to police earlier this summer, which was dealt with by Constable Mel Twyman.

Lake Hawea assistant harbourmaster Trev Hewson said yesterday he had also received two calls since the buoy was placed in the lake in November, neither of which were forwarded to the police because he was able to tell the callers what it was.

The callers were holiday-makers and had never seen the buoy before, he said.

Mr Hewson is the first response boat leader for the Lake Hawea marine search and rescue team.

He has attended six callouts this summer, none of which involved the buoy.

The callouts typically involved helping people in swamped or drifting boats.

No-one had come to harm.

Mr Black confirmed he had required Niwa to fit a flashing light to the metal buoy, which is anchored about 300m off the shore of Lake Hawea opposite the Lakeside Dr and Muir Rd intersection.

"It is a sizeable buoy, so it's got a light on it.

"If anyone hit it at night, it could do some damage," Mr Black said yesterday.

Mr Black said he had advised the Lake Hawea Community Association when the buoy went into the lake.

Contact Energy also issued a media release.

Mr Black said he would arrange for another radio bulletin to advise of the presence of the buoy and the flashing light in the lake.