In Genesis, the floodwaters prevailed over the earth for 150 days.
Genesis 7:24 says the waters prevailed for 150 days after the Flood began. Genesis 8:3 then says the waters gradually receded after that period. This figure is distinct from the forty days and forty nights of rain mentioned earlier in the narrative.
The chronology in Genesis contains several time markers, including Noah’s age, the date the Flood began, the month when the ark came to rest, and the eventual drying of the ground. Readers sometimes combine the forty days of rain with the entire duration of the Flood, but the text presents them as different periods.
Because biblical chronology can be translated and interpreted in more than one way, calculations of the complete time Noah spent in the ark vary. The 150-day figure itself is the specific duration given for the waters’ dominance.