Rivers and lakes across the world are often dyed green for St. Patrick's Day, but it seems Rio are celebrating about 200 days too early.
Spectators and competitors in yesterday's Olympic diving events were greeted by a rather unusual surprise, as the diving pool had changed colour from light blue to a murky green shade.
The cause of the colour change is so far a mystery.
British diver Tom Daley tweeted a picture of the pool, which showed the contrast between the green water with the light blue colour water beside it.
Ermmm...what happened?! pic.twitter.com/pdta7EpP2k
— Tom Daley (@TomDaley1994) August 9, 2016
The Olympic diving pool just randomly turned dark green, while the water polo pool next to it stayed blue. But everyone is chill about it.
— southpaw (@nycsouthpaw) August 10, 2016
It's a sign @OliverDingley 😉 #Diving pic.twitter.com/GeKmCbcuJG
— Team Ireland (@olympiccouncil) August 10, 2016
A sports reporter for The Times of London tweeted that a UK diver said she had trouble seeing her dive partner through the murky green water.
#greenpool - @toniacouch says it was so green she couldn't see dive partner @LoisToulson under the water #Rio2016
— Martyn Ziegler (@martynziegler) August 9, 2016
Water quality has been a major issue surrounding the Rio Games, but until now the concerns centred around the ocean and lagoons, and not the pools.
Olympic organisers said water tests were carried out and there was no risk to athletes, and the cause of the colour change is under investigation.
The water quality at the Maria Lenk Aquatics Centre was tested and there were no risks for the athletes. We are investigating the cause.
— Rio 2016 (@Rio2016_en) August 9, 2016
Canadian team leader Mitch Geller suspected the cause was algae that multiplied quickly in the day's warm and sunny conditions.
"Everybody was scratching their heads going, 'What's going on?'" he said, "It seemed to get worse over the course of the competition."
"It's not really dangerous. It's not like it's toxic or dirty or any of that. I think that the filter is busted, but I'm not sure," he added.
Additional reporting by IRN
