According to Genesis, the floodwaters prevailed for 150 days during the Noah's Ark story.
Genesis 7:24 states that the waters prevailed upon the earth for 150 days. This is not the same measurement as the 40 days and 40 nights of rain described earlier in the narrative.
After the 150 days, Genesis says that God caused a wind to pass over the earth and that the waters began to subside. The ark eventually came to rest, and Noah waited through additional stages before leaving it.
Readers sometimes combine the rainfall period and the water period into one figure. The text presents them as related but distinct intervals: rain falls for 40 days, while the waters remain dominant for 150 days.