Dozens more were marked red, meaning poor water quality.

Chris was relieved they hadn’t been swimming.

“[We] just wanted to enjoy the sun at the beach on our day off,” she said.

“I had no idea. I think I’m not going to swim right now, actually. I think we’re going to have to maybe drive further down to be able to swim in the sea.”

Lauren said she preferred to keep her distance from faeces, but she had seen a lot worse.

“I have very sensitive skin, especially with like folliculitis and like skin irritations, so water quality is important to me,” she said.

“I did yoga training in Bali and there was literal trash and like faecal matter in the water and I wouldn’t want to do that again. Wouldn’t recommend it.”

Thunderstorms over the weekend had filled Auckland’s wastewater infrastructure to the brim and spilled out into the harbour.

Victoria University freshwater ecologist Dr Mike Joy told Midday Report the warming climate would cause more frequent spills over time.

“You’ve got climate change, which means warmer temperatures, which means more growth of, you know, dangerous bacteria, but also more extremes in weather,” he said.

“So we get these flooding events and high rainfall events.”

He said the ageing wastewater infrastructure across New Zealand couldn’t handle the volume.

“Huge amounts of water that shouldn’t be in a sewage system that gets in through, you know, old broken infrastructure plus illegal connections, meaning massive flows, you know, additional flows coming into wastewater treatment plants and they just can’t handle it,” he said.

“They don’t have storage. They open the gates and let it out.”

At Sentinel Beach in Herne Bay, beachgoer Michael wished he could just go for a swim without ending up waist deep in waste.

“Yeah, I think that’s pretty bad… It would be nice to be able to like come down here, have a swim and know it’s safe without checking,” he said.

Auckland Council’s SafeSwim technical lead Dr Martin Neale said swimmers risked catching a nasty bacterial infection.

“The source of the contamination is pathogens in the water. So, that’s the risk you’re exposing yourself to,” he said.

“Generally, those will manifest as either respiratory or tummy upsets. But sometimes if you have a cut or something like that, it can infect the cut.”

He warned of similar interruptions throughout the rest of summer.

“During summer is when we get these sort of intense thunderstorm situations like we had yesterday, there was thunderstorm warnings out and we’ll see them in summer,” Neale said.

“We don’t know how many, but when those things do happen, we would encourage people to check out SafeSwim.”

Neale expected the contaminated waters to clear over the following two days.

In a statement, Watercare noted that it was already investing in upgrading wastewater infrastructure to reduce spills.

“We are investing $8 billion in new and upgraded wastewater infrastructure in the next decade, which includes $4.8b specifically in wastewater networks to reduce overflows,” head of wastewater Jon Piggot said.

“For Herne Bay and St Marys Bay, the real results will come around 2028 when we finish the Herne Bay Collector tunnel.”

– RNZ