Mystery Solved: Why Rio's Olympic Diving Pool Turned Green

Thursday, 11 Aug, 2016

FINA said the reason for the discoloration, which was so severe that pairs divers could not see the partner next to them when they submerged, was because the pool's water tanks "ran out of some of the chemicals" necessary for the water treatment process.

One of the most common causes of green swimming pool water is inadequate levels of chlorine.

The committee said the water had been tested and posed no risk to athletes, however some Australian water polo players complained of irritation to their eyes.

The condition of the pool worsened throughout the Australia-Japan match, but officials insist they expect the water polo pool and diving pool to be back to their regular colour by the end of the day.

Andrada said the pool color would get back to normal "very shortly".

But on Tuesday the water in the pool where the divers for the women's synchronized 10-meter platform competed - officially called a diving well - was dark green. But she said the water didn't smell or affect her skin.

Pool water should have a minimum chlorine or bromine concentration of 2.0 parts per million and a pH level between 7.2 - 7.8. The pool around them was turning green. The diving pool remains bright green. Both pools are outdoors and are heated by the sun's rays in the already warm weather.

Games officials attribute the waters to a "proliferation of algae," a naturally-occurring cyanobacteria that is often triggered by above-average water temperatures, sunshine, and, in some settings, nutrients from agricultural runoff, industry waste, and sewage.

Rio spokesman Mario Andrada stressed during a press conference Wednesday that the pool's pH and chlorine levels were within the required standards and that both pools were treated during the night, with alkaline levels improving.

However, after a day's worth of tests and examinations, officials think they have it figured out, according to Reuters.

"If algae can grow in the pool, other stuff can and is growing", Kirby says.

The problem also affected the synchronised swimming pool to a lesser degree on Tuesday with athletes puzzled and concerned.

Algae could have proliferated because of too much heat and a too little wind in the venue, CNN reported.

Athletes were unaffected by the change in colour but Mitch Geller, chief technical officer of Diving Canada said the team had brought in a pool expert to help.