The Flood, and Floodwater
"Like in the home universe, the Flood happens when things get out of control in the real world, and the normal order of it can't be mantained in its current state. Signalled by an unusual amount of cloudcover for over a week, and a faint smell of copper a few minutes before it happens, it begins with bright red rain coming down from the clouds, harder and harder with each minute that passes. Whatever's coming down from the clouds, it quickly contaminates the existing water, and before you know it, boom,
whole world's covered in red. It takes a few days for it all to recede again, and everyone who didn't already know it was coming was...well. Basically screwed.
People survived by either hiding underground or getting on specially built boats. A lot of sensitives, particularly the transmitters, already knew it was gonna happen, so they put quite a bit of research into protecting themselves from it. The use of red oil to coat surfaces that were gonna be in contact with the water was a complete shot in the dark- they're very, very lucky it worked.
Now for one thing that differentiates Bluespaceverse- the floodwater itself. The water stayed this way after the flood receded, which basically meant that outside of human settlements, the earth was gonna stay a wasteland. Its properties are identical to normal water in most ways, with two exceptions- it's severely caustic and tends to corrode and dissolve things it comes into contact with, and is also a bright, angry red. Normal tests reveal little about its nature; it seems to just be normal water in a large majority of results. What people knew at the time was that red oil protected surfaces in contact with it from corrosion, at least for a while- and it was this knowledge that kickstarted the production of decontamination facilities, for when they ran out of bottled water."