Why did the Olympic diving pool turn green?

It was a question that dominated the build-up to the diving events on Tuesday evening: why has the swimming pool turned green?

Consternation over the colour of water in the pool threatened to overshadow the women's 10m synchronised diving final on Tuesday at the Olympics.
Olympics green pool
Divers overlook the green pool at the Maria Lenk Aquatics Centre CREDIT: ADAM PRETTY/GETTY IMAGES
Far from the glimmering blue seen in Monday's men's event, the pool was an increasingly murky green as the women progressed through their dives, and nobody was clear on why the water has transformed in colour.

Commentators could only speculate as to what had caused the "green abyss", as the BBC team termed it, while spectators channelled their alarm on social media.

Theories from algae, to urine were offered up on social media and, while Olympic organisers assured the public the water was safe for competition, they admitted they were unsure what the cause was.