The waters receded from the earth continually. After the end of one hundred fifty days the waters decreased.
Referenced Verses
Gen 7:24 : 24 The waters prevailed on the earth one hundred fifty days.
Gen 7:11 : 11 In the six hundredth year of Noah's life, in the second month, on the seventeenth day of the month, on the same day all the fountains of the great deep were burst open, and the sky's windows were opened.