What does Genesis 7:21 mean?
Up to this point in the story of the flood, the focus has stayed with the ark, and with the eventual survivors. Now it moves to clearly indicate what happened to everything left outside of the ark. In short, everything died. The verse lists some of those groups: birds, livestock, beasts, wild animals, and swarming creatures, along with every single human being. While some debate whether or not this was a local or global event, this verse makes the outcome of this event explicitly clear: not a single person survived this disaster, other than those aboard the ark.The experience of those first moments while the waters rose must have been truly terrible. Those aboard the ark were finding out, in the critical moment, whether or not this vessel would support them. As promised, of course, it did (Genesis 7:17). An additional source of nerves would have been the ark's lack of control. This structure was not a "ship," and had no oars, sails, or rudders. It was simply a waterproof box. But, since it was designed by God (Genesis 6:14–16), and sealed by God (Genesis 7:16), it served its purpose well.
The end result of this deluge was final and absolute. Everything died, except for the remnant on the ark adrift on a single, vast ocean.