Peter is referring once again to the flood (Genesis 6—9, see also 2 Peter 2:5). With the flood, the earth which came out of the water was once again covered by water. This one event from history completely contradicts the claim that all things have continued the same since creation. It also serves as a confirmation of future judgment to come since it is an example that God intervenes in this world and keeps his promises (in this case, the promises he made to Noah).1
6 and that by means of these the world that then existed was deluged with water and perished.