At the beginning of the 2016 Olympic Games in Rio de Janeiro, viewers were puzzled by the red circles that were visible on the bodies of members of the U.S. swimming team, which turned out to be caused by an ancient Chinese medicine practice called "cupping therapy."
Then, viewers of the Aug. 9 diving competition wondered why the pool water suddenly turned green, the Daily Mail reports.
British diver Tom Daley, winner of the bronze medal, summed it up by tweeting: “Ermm.. what happened?" He also took a photo that reveals the obvious difference between the green diving pool and the blue swimming pool, which is next to it, reports The New York Times.
Despite the murky green color, a spokesman for the International Olympic Committee said the water was tested and concluded that it presents “no risk whatsoever” to the divers.
The green color is caused by “a proliferation of algae,” said organizing committee spokesman Mario Andrada, who added that “This was because of heat and a lack of wind ... We did all the chemical tests. The pool will be blue today.”
Andrada seemingly contradicted himself when he also said: “We don't know exactly what happened,” and that the diving pool water was tested “using the same parameters we do every day, and the results were exactly the same as we got when the pool was blue.”
The diving pool is kept warmer than the swimming pool, and that combined with the bright Rio sunshine leads to the evaporation of chlorine, Daily Mail notes.
Ralph Riley, of the UK Pool Water Treatment Advisory Group, added: “It needs the chlorine disinfectant to be clear, bright, blue and sparkling, so if it's not there, the water could become discolored.”
Naturally, other theories for the color spread throughout social media, ranging from corroded pipes to excessive urination.