How does physical evidence show that a flood covered the earth?

Ninety percent of the earth's surface is covered by sedimentary rock. This is the type of rock that is formed by water. Sandstone, limestone, conglomerates, etc. are all present in very large quantities on the surface. When we build a new road through the mountains, cut clefts, and expose rock layers, most often they are sedimentary. This type of rock is so common that it is very likely that most people have never seen any other type of rock. Now the skeptics say that some of these rocks could not be formed in a flood, but they still say that water was necessary, and during the flood, we had plenty of water!