The mountains rose and the valleys sank.
Simple really - see hydroplate theory. Wait, never mind, I forgot you two are all about criticizing rather than reading and trying to understand what you don’t...or rather choose not to understand.
LOL, you do understand that the Earth’s crust floats over a spherical layer of liquified rock, don’t you? There is a reason why the continents on Earth today have coastal outlines which match closely with the coastlines across the oceans - western Africa with South America, eastern North America with northern Africa - the observation upon which modern plate tectonic theory was based on. What these two points imply is that the crust cannot simply rise or fall like you imagine, and that the landmass has more or less retained shape for aeons.
There is no evidence for the Earth being covered completely by water - zip, nada. Even the title of this article is misleading - the floods mentioned therein are all local floods, repetitive and not a singular, global event. If these were Noah’s “flood” then there would have to be hundreds, if not thousands, of Noahs, to gather all the fauna of Earth in rickety wooden dinghy-like boats, to “save” them during each one of these “Biblical” floods.