This time, it's the water polo pool.
On Tuesday, when the diving pool at the Maria Lenk Aquatics Centre mysteriously changed colors, Olympic organizers and FINA -- swimming's international governing body -- offered competing explanations why.
On Wednesday, the water polo pool at the center also went green.
Swimming pools, in case anyone is unclear, are supposed to be a shade of azure.
So, what is going on? There are many explanations.
A change in alkalinity:
Mario Andrada, the communication director for the Rio 2016 local organizing committee, says a sudden change in alkalinity is the culprit.
"We expect the color to be back to blue soon," Andrada said, adding there is "absolutely no risk to the athletes or anybody."
An algae bloom:
Nope, the green tone seen was due to a proliferation of algae, the organizing body said. The algae bloomed because of heat and lack of wind, it said.
Nope, says, FINA, the blames lies with the organizers. FINA claims water tanks "ran out some of the chemicals used in the water treatment process." It made no mention of wind or heat.
The Internet dives in
It didn't take long for the Internet to offer up its own imaginative take on the green shade.
Commenters joked that it was nice of Shrek to loan his swamp to the Olympics, while others shared pictures of Kermit the frog and swamp monsters.