The image is striking and shows that the oceans, while deep, are really quite shallow with respect to the planet as a whole. In fact, they are more like a thin layer covering it.
More striking is the amount - or lack thereof - of fresh water. If you follow the second link of the opening sentence and go to the USGS's web site, it explains how the second-largest blue sphere on the image is the amount of fresh ground water and that most of it is inaccessible. The diameter of the sphere is about 170 miles and its volume is approximately 2,551,100 cubic miles. That is not a lot for a planet of 7 billion.
There is more data on the actual web page and I highly encourage you to review it and let it inform how you think about water consumption and conservation. This is by far the world's most precious resource. It is depleting and it will not be long before it is the source of conflicts everywhere. Diminishing water supply is just one more vulnerability- albeit a very big one - exacerbated by man-induced climate change.
Some very interesting solutions are being proposed for dealing with this challenge. Like many forward-thinking answers, however, it will take a lot of support - largely in the form of R&D - to scale it to meet the size of the problem. But we can do it. Let's hope we do it before we absolutely have to.