It is nicer with the jagged coastlines, and no dirt. Did you intend for the deeper islands to have black sand around their edges? Just pointing out that it's different from the rest of the map, not necessarily bad. Um, your mountains... =) haha (as a last resort, you could try inverting the layer). I'm not sure what style/process the tutorial follows, but you could always draw them by hand, too, with various brush-style settings. That's my habit, but it's not to everyone's liking.