Actually, both.
Genesis 7:
11In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened.
12And the rain was upon the earth forty days and forty nights.
I think there was some kind of water in the atmosphere, too. Kept the earth “moist” and protected the planet from solar radiation - could account for the long lives of people during the time. Less radiation, less nuclear degradation.