Why isn't the ocean deeper at its center? I need this answered soon!

Because some rock grinds down and some does not so that is why it is not deeper in the middle also floods.

The surface of the Earth below the oceans is not evenly spread in planes and depressions. At some places, it is low-lying and at some other places, it is elevated. That is why the ocean is not deeper at its center.

Explanation:

During the formation of the Earth around 4.5 billion years ago, it was a gigantic mass having a non-uniform structure and a highly uneven surface. The Earth was later cooled down by rains that poured down for thousands of years continuously. These rains filled up the low-lying parts of the Earth which then resulted in the formation of a huge unibody of water that we today classify as oceans. When the Earth was formed, its deepest depressions weren't formed at its center. That is only why the ocean is not the deepest at its center.