“In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened … And the waters prevailed on the earth 150 days.” (Genesis 7:11+24)
When God tells Noah it’s time to enter the ark, he and his family, together with all those animals, go in. God Himself shuts the door. This is the point of no return. Everybody who is not in the ark by then, will die. And everybody who is in the ark, will have to stay there till the judgment is over!
The Bible records that “all the fountains of the great deep burst forth and the windows of the heavens were opened”. This clearly is a supernatural phenomenon, used by God to destroy all living things. An incredible amount of water covers the earth, until even the highest mountains are covered. This situation lasts for 150 days, and then the water starts to go down. But it takes over half a year before the earth is has dried sufficiently for Noah and his family to leave the ark. All in all, they have been locked up for about one year…
Maybe they wondered whether this situation would ever end at all. But Genesis 8:1 (ERV) explicitly remarks: “God did not forget about Noah. God remembered him and all the animals that were with him in the boat.” On the 27th day of the 2nd month, they could finally leave the ark. God always keeps his promises!