What does it take to remove the salt from ocean water. I was just thinking if this were possible and cost-effective, it could solve the world's water shortage porblems. What's stopping us?

http://en.wikipedia.org/wiki/Desalination

 

It is used. The problem is mostly just that it's so energy intensive and requires a lot of infrastructure, and that regions with shortages of clean, fresh water don't have the resources for it. It's used most extensively in the Middle East, where of course energy is cheap and water is scarce. "The world," of course, has no water shortage, per se. As you've noticed, most of the planet is covered with the stuff a few miles deep, it falls from the sky, and it's 100% recyclable.

But it can be done, right?

yes it can be done but in most cases it is not cost effective.