Basically, because the earth is rotating, the oceans bulge around the equator by about 5 miles. In the absence of this rotation, the water levels would redistribute toward the poles, submerging most of North America, Europe and northern Asia. It would also cause land that was previously in the bottom of the ocean around the equator to be above the surface, creating a continuous ring of land separating a Northern and Southern ocean. I love things like this!
I recently came across this map in one of my favorite cartographic blogs. It shows the result of a simulation shown here, based on 3-D surface modeling, of what the earth's surface would look like in the absence of centrifugal force caused by our planet's rotation.