What percentage of Earth's surface is covered by water?

About 71% of Earth's surface is covered by water, but 97% of that is salt water. Of the roughly 2.5% that is fresh, about 69% is locked in glaciers and ice caps and most of the rest is groundwater. Lakes and rivers hold only about 0.3% of fresh water, so readily accessible surface fresh water is around 0.01% of all water on Earth.

Source: USGS, Where is Earth's water?; Shiklomanov (1993)