Story highlights Algae to blame for green hue of Olympic pool

Or is it alkalinity?

Rio (CNN) There's something in the water at the Rio Olympics: Yet another pool has turned deep, bright green.

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.

The water of the diving pool at right appears a murky green as the water polo pool at left appears a greener colour than the previous day.

On Wednesday, the water polo pool at the center also went green.

An inspector takes a sample from the water polo pool which turned green in color.

Swimming pools, in case anyone is unclear, are supposed to be a shade of azure.