FRESH water. It's a lake. Maybe 40 quadrillion is an exaggeration, but with Berkey filtration, our fresh water supply is effectively unlimited.
When I think about prep, water is #1, even before lead and brass, although we've pretty much got that covered as well.
I took your 40 quadrillion literally. Since the Atlantic Ocean has under 100 billion gallons, I should have know you were exaggerating.
I agree that water is #1 for prepping. I just decided that in the case of certain types of disasters, I may just die.