What if every human died.

You'd cover the entire earth in 0.0007 millimeters of water.

Not much of a flood, huh?

The actual value is even smaller, because the way Random_Overlord calculated the average overestimated the amount of water to be dumped into the system. Using his numbers:

(60 kg + 70 kg)/2 * (0.55 + 0.78)/2 * 6,697,254,041 = 28,948,880,592 kg

If the surface of the earth is 5.1x10^15 m^2, and 1 L covers a m^2 to a depth of 1 mm, then the Earth would only be covered in an additional depth of 0.5676 micrometers. That's less than the diameter of a single E.coli cell.