The mystery has been solved - the International Swimming Federation (FINA) has confirmed a chemical imbalance caused the water in the Rio diving pool to go green.
On Tuesday, pictures on social media showing the previously clear pool at the Maria Lenk Aquatics Centre in a greener hue rapidly spread, prompting concerns for the safety of athletes.
The discolouration spread into the neighbouring area used for water polo by Wednesday, and FINA has clarified the issue is down to a problem in the treatment process of the water.
However, swimming's world governing body insists the pools are safe to use and do not pose a health hazard to competitors.
Ermmm...what happened?! pic.twitter.com/pdta7EpP2k-- Tom Daley (@TomDaley1994) August 9, 2016
"FINA can confirm that the reason for the unusual water colour observed during the Rio 2016 diving competitions is that the water tanks ran out some of the chemicals used in the water treatment process," an official FINA statement read.
"As a result the pH level of the water was outside the usual range, causing the discolouration.
"The FINA Sport Medicine Committee conducted tests on the water quality and concluded that there was no risk to the health and safety of the athletes, and no reason for the competition to be affected."
Rio 2016 organising committee executive director of communications Mario Andrada insisted the pools will soon return to their blue state.
He said: "A sudden change in alkalinity, that was the reason. The water polo [pool] has been affected the same way. pH levels are at the required standard. We treated both pools in the night and the alkalinity levels have improved, we expect the colour to be back to blue soon.
"People in charge could and should have done more intensive testing during the day. We brought in a team of independent experts to study the conclusions that I brought to you.
"There is absolutely no risk to the athletes or anybody - the independent experts confirmed this."