Rio 2016: The Olympic diving pool is still green despite health warnings, and may never be fixed

The bright, mysterious green of the Olympic diving pool hasn’t gone away. And that’s a big worry.

The Rio aquatic centre is now into its second day of accidentally playing host to what looks more like a diving pond or swamp than a pool. And the failure to fix the colour might indicate that the problem is bigger than had been thought.

Initially, after concern about the verdant colour of the pool, officials and experts said that the most likely cause was algae. That had been allowed to bloom because of a problem with the pool’s operation had led it to lose the chlorine that would usually keep it sparkly and blue, they said.

But if that were the problem then fixing the chlorine levels by pouring new chemicals into the pool and making sure they were diffused would get it back to health. That has not happened, and the pool continues to be green – although potentially a slightly less lush hue, according to some that have seen it.

In some pictures and footage, the other pool – used for water polo and synchronised swimming – appears to be turning slightly turqouise. But that seems largely to be a trick of the light and the reflection of the colour coming from the branding at the side of the pool.

On the first day of the green pool, officials said that they had the problem under control and that it was about to be fixed. The issue was a “proliferation of algae”, said Rio spokesman Mario Andrada, and so would be fixed with treatment.

"This was because of heat and a lack of wind," he said. "We did all the chemical tests. The pool will be blue today.

"If it were green and yellow, we would know it was a patriotic thing," Andrada joked, referring to Brazil's national colours.

Pool treatment experts had suggested the same, predicting that a quick shock treatment of chlorine would clear up the pool.

Though the algae that is thought to have caused the colour isn't necessarily dangerous in itself, it can lead to other problems. Those concerns have led experts to say that they wouldn't go in the pool, given the chance.