On Wednesday, the Otago Regional Council advised, in a statement, people not to swim in the lake at the testing site by the Lake Hāwea Holiday Park.
According to the council, water quality tests showed high levels of bacteria.
They also advised people to avoid swimming in the lake 48 hours after any rain.
The council said yesterday it was not aware of a specific pollution event at this site associated with this result.
The lake was generally safe for swimming, as reflected by its "excellent" long-term grade on Land, Air, Water Aotearoa.
This was just the second occasion in the last five years of summer monitoring where results at this site have been "unsuitable for swimming".
Further testing would be carried out on Monday.
The warnings did not stop some travellers and Lake Hāwea residents from continuing to swim in the lake yesterday.
One group of Hāwea residents had brought their boat to the Lake Hāwea Holiday Park to fix which required some of them to get in the water.
Lake Hāwea resident Sasha Wetzel said he had no knowledge of the red alert or the contamination.
"You think they’d put up a sign," he said. There were no warning signs to be seen.
The holiday park entrance to the lake did not have any signage to indicate the water was temporarily not fit for swimming.
Mr Wetzel also added that he was "not surprised" the lake was currently polluted due to the council’s lack of sufficient funding over the last few years.
The warning did not seem to urge Mr Wetzel and his group to get out of the water, and he was not alone yesterday in giving the alert little thought.
A family travelling from Invercargill on holiday was also swimming in the lake yesterday afternoon.
One family member said he had been told by a friend in Wānaka to avoid swimming in the lake unless it was sunny but had not seen any other official information to pressure him into staying out of the lake.
Lake Hāwea Holiday Park staff declined to comment when approached.
By Rawan Saadi
