Here’s Why The Olympic Diving Pool Mysteriously Turned Green

Update 08/10/16: FINA, the international governing body of aquatics, released a statement Wednesday afternoon attributing the discoloration of the water to its pH levels rather than algae. Read more here

Something is very wrong with the Olympic diving pool. Out of nowhere, it has turned a bilious shade of green, more akin to green Kool-Aid than anything in which the world’s most elite athletes should be swimming.

Though the diving pool was its usual shade of crystalline blue on Monday, attendees and divers woke Tuesday to decidedly emerald-hued waters, sparking the Twitter hashtag #greenpool and a myriad of theories as to what happened.

The pool was tested to make sure the water was safe for the athletes. While it was deemed safe, they were instructed not to open their mouths underwater—just in case.

Today, it was revealed that the color was due to an algae bloom that officials are blaming on the “heat and a lack of wind.” In a statement released to the media, the committee stressed that the water was tested and there was no risk to athletes. It also said the pool should be back to its normal color for today’s events.

Although the green water was considered safe, it did pose an issue for some athletes. According to interviews with several divers, the water was so dark that the bottom of the diving pool was not visible.

You may notice, there are usually water jets or bubbles dispersed across the diving well. Why? The movement causes a disturbance in the water, helping divers more accurately judge their distance (or height) from the surface of the water.

The Chinese duo Chen Ruolin and Liu Huixia said the green water didn’t affect their ability to take gold in the event. Canada team leader Mitch Geller said in an interview with the Associated Press that underwater visibility is very important.