According to Genesis, the floodwaters prevailed over the earth for 150 days before they began to recede.
Genesis 7:24 states that the waters prevailed for 150 days, and Genesis 8:3 then says they began to abate. This figure is separate from the forty days and nights of rain mentioned earlier. The distinction explains why the flood narrative contains several different time spans that are sometimes collapsed into one.
Genesis continues with a detailed sequence of dates: the ark comes to rest, the mountain tops become visible, and Noah eventually sends out birds before leaving the vessel. These chronological markers give the account a structured timeline rather than presenting the flood as one undifferentiated event.
Different readings of the Hebrew calendar and chronology can affect how readers calculate the total episode, but the stated period of prevailing waters is 150 days. That is the specific figure in Genesis 7:24.