Making Seas

I've seen some maps where they have the names of bodies of water such as Hudson Bay or Mediterranean Sea without them being countries. How do you do this?

You go to the countries selection at the top of the screen or select a piece of land. Click add country. Name it and save it, not on land, of course. And next to the name should be a button called Set which allows you to set the name anywhere you want.

Thank you!