The divers at the 2016 Rio Olympics were landing in pristine, well-maintained, crystal-clear blue water on Monday.

Well, a lot can change in a day.

During Tuesday's competition, many noticed something ... different ... about the water.

Why is the synchro dive pool green? The one next to it looks normal. #Rio2016#cbcpic.twitter.com/m46IqE70Hd — David Common (@davidcommon) August 9, 2016

Something fishy about the colour of the water in the diving pool just now. Water polo beside it quite a contrast. pic.twitter.com/0mbcrdQPGl — Orla Chennaoui (@SkyOrla) August 9, 2016

Here's an idea of just how green the diving pool has turned... https://t.co/imZ9mQJ1j8#Rio2016pic.twitter.com/RQO2Dekgsx — BBC Sport (@BBCSport) August 9, 2016

#greenpool - @toniacouch says it was so green she couldn't see dive partner @LoisToulson under the water #Rio2016 — Martyn Ziegler (@martynziegler) August 9, 2016

There has to be some sort of rational explanation, right?

Unlike the Olympic organizers, the Twitterverse was much more forthcoming with theories about the green water.

The NFL Hall of Fame game grounds crew was also in charge of chlorinating the diving pool (Photo via @mattmajendie) pic.twitter.com/HoEpqIJXTw — RedditCFB (@RedditCFB) August 9, 2016

Our coach used to tell us as little kids: a special chemical would turn the water green if you pee in it. It worked. https://t.co/G8TBIYsQNP — Mark Spiessl (@MSpiessl) August 9, 2016

@BBCSport Green colour is caused by Copper in the local water not chlorine - copper reacts with chlorine & comes out as green, iron as red — Richard Bishop (@WellnessBishop) August 9, 2016

The Associated Press' Beth Harris reports that Rio organizers are aware of the color change (how could they not be?) but despite being unable to explain it are sure it's safe (how can they be?).

Water at diving went from clear blue to murky green in 1 day. Rio organizers can't explain it, but say it's safe. pic.twitter.com/XmWfeFGJsq — Beth Harris (@bethharrisap) August 9, 2016

While we await an official response at least we know it has to be safer than swimming in Rio's natural bodies of water ... right?