Chances are that at one point or another during your school years you would have heard the familiar cry – take a pee in the pool, and the water will turn purple, blue or whatever other colour you can think of to signify humiliation.

So did someone take a massive slash in the Olympic diving pool then? Just take a look at that mess up top, and spare a thought for those taking a plunge.

Well here’s a few (tongue in cheek) theories from the folks at Wired:

• Stealth marketing for new Olympic sponsor, Midori
• Pool always loved the Chicago River’s St. Patrick’s Day shtick
• Secret chemical that turns pee green + Russians panic-dumping samples before surprise WADA inspection
• Many people are saying that Donald Trump’s pool cleaning service is not everything the ads promise
• Synchronized divers’ microbiomes went a little rogue after that one jump, if you know what we mean
• GFP GMOs
• Water actually gold but shows up as green on new-fangled colour TVs
• A tale of eldritch horror from the benthic depths
• “Blood-colored” feels a little too on-the-nose
• U jelly?
• Caipirinha-flavored Soylent
• Brazilian pride. (The racing pool is yellow)

Now to get a little serious…

Vox took a stab at what may have caused all that green:

It’s algae

The Olympic diving pool is kept warmer than the one with the lap lanes. That means it’s a bit more of a friendly environment for microbes to grow in, as Sports Illustrated points out. But then, there ought to be enough chlorine in that pool to kill the algae. Ought to.

It’s oxidised copper

Think of the Statue of Liberty’s patina: When its copper was exposed to water, it began to oxidize [sic] (i.e., rust). Unlike iron, which turns brown when it oxidizes, copper turns green. But then how would copper get into the pool to oxidize? Is a pipe corroding?

Whatever the case, maybe there will finally be a little something to do for the lifeguard on duty…

It seems like lifeguarding at the swimming events ain’t all it’s cracked up to be…

[sources:wired&vox]