I saw this image in a Gizmodo story called “Most Habitable Earth-Like Planets May Be Waterworlds,” by George Dvorsky. I had to steal it … but since the USGS provided the image, it’s not stealing at all.
Take all the water on the surface of the Earth and put it all together in one mammoth drop. The above image shows what you’d get. At first glimpse, it’s less than I expected. Looking more closely, the drop covers almost the full north-south distance of the continental United States. Still, it’s less than I expected.
Image courtesy of the United States Geological Survey.