Tom Daley expressed his bemusement when he spotted that the Olympic diving pool had turned green.
“Ermmm...what happened?!” the bronze medalist tweeted.
For those who have no idea what we’re on about, images have surfaced of the water inside the Maria Lenk Aquatics Centre, the arena being used for swimming and diving events at the Rio Olympic Games, turning from blue to green.
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Folk on social media have been speculating about the cause of the colour change, many hilariously wondering if it’s urine.
Other possibilities include an overabundance of algae, while some even joked that the water had been dyed green to represent the Brazilian flag.
It's not urine
An investigation is taking place but one option that can be ruled out is, unsurprisingly, urine.
“It’s way too big,” Brett Blair, a national manager of Jim’s Pool Care, told The Guardian.
According to Rio spokesman Mario Andrada “a proliferation of algae,” caused the green water.
"This was because of heat and a lack of wind," he said, per the Independent. "We did all the chemical tests. The pool will be blue tomorrow (Wednesday).
"If it were green and yellow, we would know it was a patriotic thing," Andrada joked, referencing Brazil's national colours.
There are different theories floating around, however. Some wonder if the pool’s filtration system failed, or struggled to handle the pool’s large capacity.
Other science nerds speculate that the presence of copper ions caused an unbalanced pH level.
Fortunately, we can 100 per cent rule out that it was urine.