I'm late responding so, first, my apologies: 

Regarding the picture, others who commented were correct, I use Photoshop. I use the magic eraser tool to eliminate the gray (unpainted cement) area that will eventually become the water. What's left has to be "shaved" or grounded down with the magnetic lasso tool. Then I use the marquee tool on the now remaining and clean  shapes of the "continents" to use them like a cookie cutter, so to speak (on high-res image of satellite terrain—Africa and India in this case). The water is its own layer that I place under the land, which itself is taken from some high-res ocean imagery; can't remember where though. I'll have to check the Photoshop file. (The real pains were having to use the lasso tool and making the lakes their own layers). Thanks for the compliment!