People are still getting into the water at Whanganui's Lake Wiritoa - despite signs warning them to keep away.

Signs have been up for two weeks, due to an algal bloom that was twice the density recommended for swimming. People were even warned not to touch the water, and to wash and gut any fish before eating them.

Then the algal density dropped dramatically, but soon after that Horizons Regional Council got word that a water sample tested on December 11 found a toxin that can damage the livers of people who swallow the water.

The toxin was at levels 1.5 times the maximum for swimming.

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Because the toxin can linger, Horizons' water spokesman wants signs to stay up until another sample can be tested this week. Results will be in by January 3.

"I understand it is frustrating for users, but we are talking about risks to your health and a precautionary approach seems very sensible in the circumstances," he said.

Despite that, one woman at the lake on December 30 was putting lifejackets on her children before they went in the water.

"We are going to wash the kids off afterwards, but we are going in," she said.

The lake is set up for use by waterskiers, kayakers and swimmers. Weed has been cleared and a pontoon and jumping ramp installed.

The water temperature has topped 20C, and tiny green particles can be seen floating in it.

It's the clearest it has looked in weeks, Jackie Dowman said. She and husband Darryl are the new owners of Lakelands Holiday Park, the former Scoutlands property at the lake's edge.

She said the lake had a faint smell when algae levels were high, but that has gone now.

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People have been swimming and waterskiing. Children at the holiday park also have a paddling pool the Dowmans have filled with bore water.

The lake always gets an algal bloom before Christmas, Dowman said. She keeps campers up to date with results of the water testing done by Horizons.

There's a row of caravans, tents and campers at Lakelands. Some visitors have cut their time at the lake short because of the warnings - but most are enjoying themselves.

"Everybody's in cruise mode and it's really good," Darryl Dowman said.