That issue took center stage on Tuesday when the Olympic diving pool that was crystal blue for men’s events on Monday had turned unsettlingly murky and green overnight.
The water quality was so bad that one diver told reporter Martyn Ziegler that she couldn’t see her dive partner under water.
A side-by-side comparison shared by Deadspin on Twitter shows just how much changed by the time women’s events began on Tuesday.
The drastic change has left athletes, Olympic organizers, the media and spectators around the world befuddled. When asked about the change, one Olympic official told reporter Matt Majendie, “it wasn’t green this morning.”
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Many have speculated that the change is due to an algae bloom that could have resulted from a lack of chlorine. A comparison between the pool used for swimming, just feet away from the diving pool and still a clean, crisp blue, supports this hypothesis.
The water in diving pools is typically five to ten degrees warmer than the water in pools used for swimming, Sports Illustrated points out. As warmer water is more conducive to algae growth, the discrepancy in the state of the pools is solid evidence that algae might be to blame.
The International Olympic Committee will reportedly release an official statement on the green pool on Tuesday afternoon, according to BBC Sports reporter Nick Hope. An official assured Hope that water tests were conducted and “there was found to be no risk to athlete’s health.”